Iterators.java revision 7dd252788645e940eada959bdde927426e2531c9
1090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson/* 21d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Copyright (C) 2007 The Guava Authors 3090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 4090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Licensed under the Apache License, Version 2.0 (the "License"); 5090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * you may not use this file except in compliance with the License. 6090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * You may obtain a copy of the License at 7090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 8090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * http://www.apache.org/licenses/LICENSE-2.0 9090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 10090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Unless required by applicable law or agreed to in writing, software 11090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * distributed under the License is distributed on an "AS IS" BASIS, 12090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * See the License for the specific language governing permissions and 14090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * limitations under the License. 15090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 16090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 17090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonpackage com.google.common.collect; 18090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 191d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport static com.google.common.base.Preconditions.checkArgument; 201d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport static com.google.common.base.Preconditions.checkNotNull; 211d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport static com.google.common.base.Preconditions.checkState; 221d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 231d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport com.google.common.annotations.Beta; 24090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport com.google.common.annotations.GwtCompatible; 25090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport com.google.common.annotations.GwtIncompatible; 26090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport com.google.common.base.Function; 277dd252788645e940eada959bdde927426e2531c9Paul Duffinimport com.google.common.base.Joiner; 28090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport com.google.common.base.Objects; 291d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport com.google.common.base.Optional; 30090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport com.google.common.base.Preconditions; 31090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport com.google.common.base.Predicate; 32090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport com.google.common.base.Predicates; 33090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 34090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport java.util.Arrays; 35090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport java.util.Collection; 36090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport java.util.Collections; 371d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport java.util.Comparator; 38090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport java.util.Enumeration; 39090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport java.util.Iterator; 40090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport java.util.List; 417dd252788645e940eada959bdde927426e2531c9Paul Duffinimport java.util.ListIterator; 42090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport java.util.NoSuchElementException; 431d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport java.util.PriorityQueue; 441d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport java.util.Queue; 45090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 46090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport javax.annotation.Nullable; 47090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 48090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson/** 49090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * This class contains static utility methods that operate on or return objects 50090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * of type {@link Iterator}. Except as noted, each method has a corresponding 51090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@link Iterable}-based method in the {@link Iterables} class. 52090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 531d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p><i>Performance notes:</i> Unless otherwise noted, all of the iterators 541d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * produced in this class are <i>lazy</i>, which means that they only advance 551d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * the backing iteration when absolutely necessary. 561d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 577dd252788645e940eada959bdde927426e2531c9Paul Duffin * <p>See the Guava User Guide section on <a href= 587dd252788645e940eada959bdde927426e2531c9Paul Duffin * "http://code.google.com/p/guava-libraries/wiki/CollectionUtilitiesExplained#Iterables"> 597dd252788645e940eada959bdde927426e2531c9Paul Duffin * {@code Iterators}</a>. 607dd252788645e940eada959bdde927426e2531c9Paul Duffin * 61090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @author Kevin Bourrillion 62090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @author Jared Levy 631d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 2.0 (imported from Google Collections Library) 64090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 651d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert@GwtCompatible(emulated = true) 66090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonpublic final class Iterators { 67090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson private Iterators() {} 68090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 697dd252788645e940eada959bdde927426e2531c9Paul Duffin static final UnmodifiableListIterator<Object> EMPTY_LIST_ITERATOR = new UnmodifiableListIterator<Object>() { 707dd252788645e940eada959bdde927426e2531c9Paul Duffin 717dd252788645e940eada959bdde927426e2531c9Paul Duffin public boolean hasNext() { 727dd252788645e940eada959bdde927426e2531c9Paul Duffin return false; 737dd252788645e940eada959bdde927426e2531c9Paul Duffin } 747dd252788645e940eada959bdde927426e2531c9Paul Duffin 757dd252788645e940eada959bdde927426e2531c9Paul Duffin public Object next() { 767dd252788645e940eada959bdde927426e2531c9Paul Duffin throw new NoSuchElementException(); 777dd252788645e940eada959bdde927426e2531c9Paul Duffin } 787dd252788645e940eada959bdde927426e2531c9Paul Duffin 797dd252788645e940eada959bdde927426e2531c9Paul Duffin public boolean hasPrevious() { 807dd252788645e940eada959bdde927426e2531c9Paul Duffin return false; 817dd252788645e940eada959bdde927426e2531c9Paul Duffin } 827dd252788645e940eada959bdde927426e2531c9Paul Duffin 837dd252788645e940eada959bdde927426e2531c9Paul Duffin public Object previous() { 847dd252788645e940eada959bdde927426e2531c9Paul Duffin throw new NoSuchElementException(); 857dd252788645e940eada959bdde927426e2531c9Paul Duffin } 867dd252788645e940eada959bdde927426e2531c9Paul Duffin 877dd252788645e940eada959bdde927426e2531c9Paul Duffin public int nextIndex() { 887dd252788645e940eada959bdde927426e2531c9Paul Duffin return 0; 897dd252788645e940eada959bdde927426e2531c9Paul Duffin } 907dd252788645e940eada959bdde927426e2531c9Paul Duffin 917dd252788645e940eada959bdde927426e2531c9Paul Duffin public int previousIndex() { 927dd252788645e940eada959bdde927426e2531c9Paul Duffin return -1; 937dd252788645e940eada959bdde927426e2531c9Paul Duffin } 947dd252788645e940eada959bdde927426e2531c9Paul Duffin }; 957dd252788645e940eada959bdde927426e2531c9Paul Duffin 967dd252788645e940eada959bdde927426e2531c9Paul Duffin /** 977dd252788645e940eada959bdde927426e2531c9Paul Duffin * Returns the empty iterator. 987dd252788645e940eada959bdde927426e2531c9Paul Duffin * 997dd252788645e940eada959bdde927426e2531c9Paul Duffin * <p>The {@link Iterable} equivalent of this method is {@link 1007dd252788645e940eada959bdde927426e2531c9Paul Duffin * ImmutableSet#of()}. 1017dd252788645e940eada959bdde927426e2531c9Paul Duffin */ 1027dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> UnmodifiableIterator<T> emptyIterator() { 1037dd252788645e940eada959bdde927426e2531c9Paul Duffin return emptyListIterator(); 1047dd252788645e940eada959bdde927426e2531c9Paul Duffin } 105090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 106090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 107090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns the empty iterator. 108090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 109090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The {@link Iterable} equivalent of this method is {@link 1101d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * ImmutableSet#of()}. 111090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 112090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // Casting to any type is safe since there are no actual elements. 113090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @SuppressWarnings("unchecked") 1147dd252788645e940eada959bdde927426e2531c9Paul Duffin static <T> UnmodifiableListIterator<T> emptyListIterator() { 1157dd252788645e940eada959bdde927426e2531c9Paul Duffin return (UnmodifiableListIterator<T>) EMPTY_LIST_ITERATOR; 116090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 117090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1187dd252788645e940eada959bdde927426e2531c9Paul Duffin private static final Iterator<Object> EMPTY_MODIFIABLE_ITERATOR = new Iterator<Object>() { 1197dd252788645e940eada959bdde927426e2531c9Paul Duffin public boolean hasNext() { 1207dd252788645e940eada959bdde927426e2531c9Paul Duffin return false; 1217dd252788645e940eada959bdde927426e2531c9Paul Duffin } 122090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1237dd252788645e940eada959bdde927426e2531c9Paul Duffin public Object next() { 1247dd252788645e940eada959bdde927426e2531c9Paul Duffin throw new NoSuchElementException(); 1257dd252788645e940eada959bdde927426e2531c9Paul Duffin } 126090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1277dd252788645e940eada959bdde927426e2531c9Paul Duffin public void remove() { 1287dd252788645e940eada959bdde927426e2531c9Paul Duffin throw new IllegalStateException(); 1297dd252788645e940eada959bdde927426e2531c9Paul Duffin } 1307dd252788645e940eada959bdde927426e2531c9Paul Duffin }; 131090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 132090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 133090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns the empty {@code Iterator} that throws 134090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@link IllegalStateException} instead of 135090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@link UnsupportedOperationException} on a call to 136090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@link Iterator#remove()}. 137090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 138090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // Casting to any type is safe since there are no actual elements. 139090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @SuppressWarnings("unchecked") 140090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson static <T> Iterator<T> emptyModifiableIterator() { 141090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return (Iterator<T>) EMPTY_MODIFIABLE_ITERATOR; 142090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 143090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 144090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** Returns an unmodifiable view of {@code iterator}. */ 1457dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> UnmodifiableIterator<T> unmodifiableIterator(final Iterator<T> iterator) { 146090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(iterator); 1471d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert if (iterator instanceof UnmodifiableIterator) { 1481d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return (UnmodifiableIterator<T>) iterator; 1491d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 150090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new UnmodifiableIterator<T>() { 1517dd252788645e940eada959bdde927426e2531c9Paul Duffin 152090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasNext() { 153090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.hasNext(); 154090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1557dd252788645e940eada959bdde927426e2531c9Paul Duffin 156090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public T next() { 157090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.next(); 158090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 159090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 160090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 161090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 162090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 1631d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Simply returns its argument. 1641d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 1651d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @deprecated no need to use this 1661d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 10.0 1671d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 1687dd252788645e940eada959bdde927426e2531c9Paul Duffin @Deprecated 1697dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> UnmodifiableIterator<T> unmodifiableIterator(UnmodifiableIterator<T> iterator) { 1701d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return checkNotNull(iterator); 1711d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 1721d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 1731d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 174090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns the number of elements remaining in {@code iterator}. The iterator 175090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * will be left exhausted: its {@code hasNext()} method will return 176090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code false}. 177090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 178090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static int size(Iterator<?> iterator) { 179090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson int count = 0; 180090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (iterator.hasNext()) { 181090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson iterator.next(); 182090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson count++; 183090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 184090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return count; 185090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 186090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 187090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 188090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns {@code true} if {@code iterator} contains {@code element}. 189090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 1907dd252788645e940eada959bdde927426e2531c9Paul Duffin public static boolean contains(Iterator<?> iterator, @Nullable Object element) { 191090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (element == null) { 192090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (iterator.hasNext()) { 193090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (iterator.next() == null) { 194090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return true; 195090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 196090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 197090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } else { 198090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (iterator.hasNext()) { 199090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (element.equals(iterator.next())) { 200090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return true; 201090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 202090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 203090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 204090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return false; 205090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 206090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 207090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 208090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Traverses an iterator and removes every element that belongs to the 209090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * provided collection. The iterator will be left exhausted: its 210090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code hasNext()} method will return {@code false}. 211090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 212090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param removeFrom the iterator to (potentially) remove elements from 213090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param elementsToRemove the elements to remove 2141d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @return {@code true} if any element was removed from {@code iterator} 215090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 2167dd252788645e940eada959bdde927426e2531c9Paul Duffin public static boolean removeAll(Iterator<?> removeFrom, Collection<?> elementsToRemove) { 217090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(elementsToRemove); 218090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson boolean modified = false; 219090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (removeFrom.hasNext()) { 220090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (elementsToRemove.contains(removeFrom.next())) { 221090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson removeFrom.remove(); 222090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson modified = true; 223090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 224090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 225090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return modified; 226090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 227090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 228090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 229090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Removes every element that satisfies the provided predicate from the 230090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterator. The iterator will be left exhausted: its {@code hasNext()} 231090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * method will return {@code false}. 232090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 233090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param removeFrom the iterator to (potentially) remove elements from 234090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param predicate a predicate that determines whether an element should 235090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * be removed 236090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @return {@code true} if any elements were removed from the iterator 2371d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 2.0 238090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 2397dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> boolean removeIf(Iterator<T> removeFrom, Predicate<? super T> predicate) { 240090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(predicate); 241090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson boolean modified = false; 242090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (removeFrom.hasNext()) { 243090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (predicate.apply(removeFrom.next())) { 244090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson removeFrom.remove(); 245090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson modified = true; 246090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 247090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 248090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return modified; 249090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 250090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 251090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 252090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Traverses an iterator and removes every element that does not belong to the 253090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * provided collection. The iterator will be left exhausted: its 254090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code hasNext()} method will return {@code false}. 255090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 256090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param removeFrom the iterator to (potentially) remove elements from 257090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param elementsToRetain the elements to retain 2581d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @return {@code true} if any element was removed from {@code iterator} 259090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 2607dd252788645e940eada959bdde927426e2531c9Paul Duffin public static boolean retainAll(Iterator<?> removeFrom, Collection<?> elementsToRetain) { 261090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(elementsToRetain); 262090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson boolean modified = false; 263090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (removeFrom.hasNext()) { 264090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!elementsToRetain.contains(removeFrom.next())) { 265090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson removeFrom.remove(); 266090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson modified = true; 267090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 268090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 269090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return modified; 270090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 271090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 272090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 273090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Determines whether two iterators contain equal elements in the same order. 274090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * More specifically, this method returns {@code true} if {@code iterator1} 275090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * and {@code iterator2} contain the same number of elements and every element 276090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * of {@code iterator1} is equal to the corresponding element of 277090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code iterator2}. 278090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 279090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>Note that this will modify the supplied iterators, since they will have 280090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * been advanced some number of elements forward. 281090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 2827dd252788645e940eada959bdde927426e2531c9Paul Duffin public static boolean elementsEqual(Iterator<?> iterator1, Iterator<?> iterator2) { 283090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (iterator1.hasNext()) { 284090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!iterator2.hasNext()) { 285090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return false; 286090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 287090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Object o1 = iterator1.next(); 288090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Object o2 = iterator2.next(); 289090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!Objects.equal(o1, o2)) { 290090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return false; 291090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 292090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 293090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return !iterator2.hasNext(); 294090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 295090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 296090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 297090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns a string representation of {@code iterator}, with the format 298090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code [e1, e2, ..., en]}. The iterator will be left exhausted: its 299090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code hasNext()} method will return {@code false}. 300090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 301090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static String toString(Iterator<?> iterator) { 3027dd252788645e940eada959bdde927426e2531c9Paul Duffin return Joiner.on(", ").useForNull("null").appendTo(new StringBuilder().append('['), iterator) 3037dd252788645e940eada959bdde927426e2531c9Paul Duffin .append(']').toString(); 304090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 305090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 306090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 307090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns the single element contained in {@code iterator}. 308090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 309090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws NoSuchElementException if the iterator is empty 310090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws IllegalArgumentException if the iterator contains multiple 311090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * elements. The state of the iterator is unspecified. 312090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 313090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> T getOnlyElement(Iterator<T> iterator) { 314090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson T first = iterator.next(); 315090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!iterator.hasNext()) { 316090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return first; 317090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 318090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 319090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson StringBuilder sb = new StringBuilder(); 320090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson sb.append("expected one element but was: <" + first); 321090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson for (int i = 0; i < 4 && iterator.hasNext(); i++) { 322090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson sb.append(", " + iterator.next()); 323090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 324090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (iterator.hasNext()) { 325090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson sb.append(", ..."); 326090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 3271d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert sb.append('>'); 328090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 329090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson throw new IllegalArgumentException(sb.toString()); 330090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 331090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 332090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 333090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns the single element contained in {@code iterator}, or {@code 334090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * defaultValue} if the iterator is empty. 335090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 336090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws IllegalArgumentException if the iterator contains multiple 337090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * elements. The state of the iterator is unspecified. 338090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 3397dd252788645e940eada959bdde927426e2531c9Paul Duffin @Nullable 3407dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> T getOnlyElement(Iterator<? extends T> iterator, @Nullable T defaultValue) { 341090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.hasNext() ? getOnlyElement(iterator) : defaultValue; 342090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 343090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 344090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 345090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Copies an iterator's elements into an array. The iterator will be left 346090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * exhausted: its {@code hasNext()} method will return {@code false}. 347090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 348090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param iterator the iterator to copy 349090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param type the type of the elements 350090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @return a newly-allocated array into which all the elements of the iterator 351090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * have been copied 352090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 3531d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @GwtIncompatible("Array.newInstance(Class, int)") 3547dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> T[] toArray(Iterator<? extends T> iterator, Class<T> type) { 355090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson List<T> list = Lists.newArrayList(iterator); 356090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return Iterables.toArray(list, type); 357090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 358090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 359090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 360090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Adds all elements in {@code iterator} to {@code collection}. The iterator 361090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * will be left exhausted: its {@code hasNext()} method will return 362090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code false}. 363090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 364090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @return {@code true} if {@code collection} was modified as a result of this 365090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * operation 366090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 3677dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> boolean addAll(Collection<T> addTo, Iterator<? extends T> iterator) { 368090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(addTo); 369090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson boolean wasModified = false; 370090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (iterator.hasNext()) { 371090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson wasModified |= addTo.add(iterator.next()); 372090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 373090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return wasModified; 374090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 375090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 376090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 377090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns the number of elements in the specified iterator that equal the 378090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * specified object. The iterator will be left exhausted: its 379090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code hasNext()} method will return {@code false}. 380090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 381090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @see Collections#frequency 382090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 383090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static int frequency(Iterator<?> iterator, @Nullable Object element) { 384090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson int result = 0; 385090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (element == null) { 386090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (iterator.hasNext()) { 387090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (iterator.next() == null) { 388090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson result++; 389090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 390090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 391090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } else { 392090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (iterator.hasNext()) { 393090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (element.equals(iterator.next())) { 394090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson result++; 395090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 396090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 397090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 398090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return result; 399090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 400090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 401090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 402090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns an iterator that cycles indefinitely over the elements of {@code 403090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterable}. 404090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 405090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned iterator supports {@code remove()} if the provided iterator 406090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * does. After {@code remove()} is called, subsequent cycles omit the removed 407090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * element, which is no longer in {@code iterable}. The iterator's 408090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code hasNext()} method returns {@code true} until {@code iterable} is 409090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * empty. 410090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 411090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p><b>Warning:</b> Typical uses of the resulting iterator may produce an 412090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * infinite loop. You should use an explicit {@code break} or be certain that 413090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * you will eventually remove all the elements. 414090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 415090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> Iterator<T> cycle(final Iterable<T> iterable) { 416090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(iterable); 417090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new Iterator<T>() { 418090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<T> iterator = emptyIterator(); 419090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<T> removeFrom; 420090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 421090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasNext() { 422090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!iterator.hasNext()) { 423090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson iterator = iterable.iterator(); 424090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 425090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.hasNext(); 426090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 4277dd252788645e940eada959bdde927426e2531c9Paul Duffin 428090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public T next() { 429090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!hasNext()) { 430090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson throw new NoSuchElementException(); 431090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 432090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson removeFrom = iterator; 433090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.next(); 434090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 4357dd252788645e940eada959bdde927426e2531c9Paul Duffin 436090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public void remove() { 4377dd252788645e940eada959bdde927426e2531c9Paul Duffin checkState(removeFrom != null, "no calls to next() since last call to remove()"); 438090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson removeFrom.remove(); 439090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson removeFrom = null; 440090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 441090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 442090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 443090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 444090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 445090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns an iterator that cycles indefinitely over the provided elements. 446090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 4477dd252788645e940eada959bdde927426e2531c9Paul Duffin * <p>The returned iterator supports {@code remove()}. After {@code remove()} 4487dd252788645e940eada959bdde927426e2531c9Paul Duffin * is called, subsequent cycles omit the removed 449090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * element, but {@code elements} does not change. The iterator's 450090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code hasNext()} method returns {@code true} until all of the original 451090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * elements have been removed. 452090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 453090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p><b>Warning:</b> Typical uses of the resulting iterator may produce an 454090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * infinite loop. You should use an explicit {@code break} or be certain that 455090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * you will eventually remove all the elements. 456090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 457090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> Iterator<T> cycle(T... elements) { 458090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return cycle(Lists.newArrayList(elements)); 459090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 460090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 461090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 462090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Combines two iterators into a single iterator. The returned iterator 463090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterates across the elements in {@code a}, followed by the elements in 464090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code b}. The source iterators are not polled until necessary. 465090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 466090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned iterator supports {@code remove()} when the corresponding 467090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * input iterator supports it. 4687dd252788645e940eada959bdde927426e2531c9Paul Duffin * 4697dd252788645e940eada959bdde927426e2531c9Paul Duffin * <p><b>Note:</b> the current implementation is not suitable for nested 4707dd252788645e940eada959bdde927426e2531c9Paul Duffin * concatenated iterators, i.e. the following should be avoided when in a loop: 4717dd252788645e940eada959bdde927426e2531c9Paul Duffin * {@code iterator = Iterators.concat(iterator, suffix);}, since iteration over the 4727dd252788645e940eada959bdde927426e2531c9Paul Duffin * resulting iterator has a cubic complexity to the depth of the nesting. 473090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 474090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @SuppressWarnings("unchecked") 4757dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> Iterator<T> concat(Iterator<? extends T> a, Iterator<? extends T> b) { 476090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(a); 477090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(b); 478090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return concat(Arrays.asList(a, b).iterator()); 479090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 480090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 481090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 482090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Combines three iterators into a single iterator. The returned iterator 483090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterates across the elements in {@code a}, followed by the elements in 484090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code b}, followed by the elements in {@code c}. The source iterators 485090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * are not polled until necessary. 486090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 487090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned iterator supports {@code remove()} when the corresponding 488090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * input iterator supports it. 4897dd252788645e940eada959bdde927426e2531c9Paul Duffin * 4907dd252788645e940eada959bdde927426e2531c9Paul Duffin * <p><b>Note:</b> the current implementation is not suitable for nested 4917dd252788645e940eada959bdde927426e2531c9Paul Duffin * concatenated iterators, i.e. the following should be avoided when in a loop: 4927dd252788645e940eada959bdde927426e2531c9Paul Duffin * {@code iterator = Iterators.concat(iterator, suffix);}, since iteration over the 4937dd252788645e940eada959bdde927426e2531c9Paul Duffin * resulting iterator has a cubic complexity to the depth of the nesting. 494090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 495090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @SuppressWarnings("unchecked") 4967dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> Iterator<T> concat(Iterator<? extends T> a, Iterator<? extends T> b, 4977dd252788645e940eada959bdde927426e2531c9Paul Duffin Iterator<? extends T> c) { 498090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(a); 499090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(b); 500090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(c); 501090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return concat(Arrays.asList(a, b, c).iterator()); 502090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 503090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 504090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 505090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Combines four iterators into a single iterator. The returned iterator 506090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterates across the elements in {@code a}, followed by the elements in 507090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code b}, followed by the elements in {@code c}, followed by the elements 508090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * in {@code d}. The source iterators are not polled until necessary. 509090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 510090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned iterator supports {@code remove()} when the corresponding 511090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * input iterator supports it. 5127dd252788645e940eada959bdde927426e2531c9Paul Duffin * 5137dd252788645e940eada959bdde927426e2531c9Paul Duffin * <p><b>Note:</b> the current implementation is not suitable for nested 5147dd252788645e940eada959bdde927426e2531c9Paul Duffin * concatenated iterators, i.e. the following should be avoided when in a loop: 5157dd252788645e940eada959bdde927426e2531c9Paul Duffin * {@code iterator = Iterators.concat(iterator, suffix);}, since iteration over the 5167dd252788645e940eada959bdde927426e2531c9Paul Duffin * resulting iterator has a cubic complexity to the depth of the nesting. 517090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 518090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @SuppressWarnings("unchecked") 5197dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> Iterator<T> concat(Iterator<? extends T> a, Iterator<? extends T> b, 5207dd252788645e940eada959bdde927426e2531c9Paul Duffin Iterator<? extends T> c, Iterator<? extends T> d) { 521090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(a); 522090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(b); 523090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(c); 524090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(d); 525090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return concat(Arrays.asList(a, b, c, d).iterator()); 526090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 527090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 528090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 529090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Combines multiple iterators into a single iterator. The returned iterator 530090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterates across the elements of each iterator in {@code inputs}. The input 531090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterators are not polled until necessary. 532090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 533090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned iterator supports {@code remove()} when the corresponding 534090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * input iterator supports it. 535090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 5367dd252788645e940eada959bdde927426e2531c9Paul Duffin * <p><b>Note:</b> the current implementation is not suitable for nested 5377dd252788645e940eada959bdde927426e2531c9Paul Duffin * concatenated iterators, i.e. the following should be avoided when in a loop: 5387dd252788645e940eada959bdde927426e2531c9Paul Duffin * {@code iterator = Iterators.concat(iterator, suffix);}, since iteration over the 5397dd252788645e940eada959bdde927426e2531c9Paul Duffin * resulting iterator has a cubic complexity to the depth of the nesting. 5407dd252788645e940eada959bdde927426e2531c9Paul Duffin * 541090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws NullPointerException if any of the provided iterators is null 542090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 543090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> Iterator<T> concat(Iterator<? extends T>... inputs) { 5441d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return concat(ImmutableList.copyOf(inputs).iterator()); 545090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 546090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 547090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 548090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Combines multiple iterators into a single iterator. The returned iterator 549090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterates across the elements of each iterator in {@code inputs}. The input 550090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterators are not polled until necessary. 551090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 552090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned iterator supports {@code remove()} when the corresponding 553090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * input iterator supports it. The methods of the returned iterator may throw 5541d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code NullPointerException} if any of the input iterators is null. 5557dd252788645e940eada959bdde927426e2531c9Paul Duffin * 5567dd252788645e940eada959bdde927426e2531c9Paul Duffin * <p><b>Note:</b> the current implementation is not suitable for nested 5577dd252788645e940eada959bdde927426e2531c9Paul Duffin * concatenated iterators, i.e. the following should be avoided when in a loop: 5587dd252788645e940eada959bdde927426e2531c9Paul Duffin * {@code iterator = Iterators.concat(iterator, suffix);}, since iteration over the 5597dd252788645e940eada959bdde927426e2531c9Paul Duffin * resulting iterator has a cubic complexity to the depth of the nesting. 560090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 5617dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> Iterator<T> concat(final Iterator<? extends Iterator<? extends T>> inputs) { 562090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(inputs); 563090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new Iterator<T>() { 564090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<? extends T> current = emptyIterator(); 565090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<? extends T> removeFrom; 566090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 567090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasNext() { 568090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // http://code.google.com/p/google-collections/issues/detail?id=151 569090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // current.hasNext() might be relatively expensive, worth minimizing. 570090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson boolean currentHasNext; 5711d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert // checkNotNull eager for GWT 5721d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert // note: it must be here & not where 'current' is assigned, 5731d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert // because otherwise we'll have called inputs.next() before throwing 5741d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert // the first NPE, and the next time around we'll call inputs.next() 5751d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert // again, incorrectly moving beyond the error. 5767dd252788645e940eada959bdde927426e2531c9Paul Duffin while (!(currentHasNext = checkNotNull(current).hasNext()) && inputs.hasNext()) { 577090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson current = inputs.next(); 578090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 579090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return currentHasNext; 580090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 5817dd252788645e940eada959bdde927426e2531c9Paul Duffin 582090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public T next() { 583090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!hasNext()) { 584090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson throw new NoSuchElementException(); 585090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 586090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson removeFrom = current; 587090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return current.next(); 588090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 5897dd252788645e940eada959bdde927426e2531c9Paul Duffin 590090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public void remove() { 5917dd252788645e940eada959bdde927426e2531c9Paul Duffin checkState(removeFrom != null, "no calls to next() since last call to remove()"); 592090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson removeFrom.remove(); 593090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson removeFrom = null; 594090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 595090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 596090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 597090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 598090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 599090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Divides an iterator into unmodifiable sublists of the given size (the final 600090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * list may be smaller). For example, partitioning an iterator containing 601090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code [a, b, c, d, e]} with a partition size of 3 yields {@code 602090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * [[a, b, c], [d, e]]} -- an outer iterator containing two inner lists of 603090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * three and two elements, all in the original order. 604090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 605090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned lists implement {@link java.util.RandomAccess}. 606090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 607090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param iterator the iterator to return a partitioned view of 608090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param size the desired size of each partition (the last may be smaller) 609090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @return an iterator of immutable lists containing the elements of {@code 610090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterator} divided into partitions 611090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws IllegalArgumentException if {@code size} is nonpositive 612090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 6137dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> UnmodifiableIterator<List<T>> partition(Iterator<T> iterator, int size) { 614090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return partitionImpl(iterator, size, false); 615090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 616090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 617090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 618090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Divides an iterator into unmodifiable sublists of the given size, padding 619090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * the final iterator with null values if necessary. For example, partitioning 620090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * an iterator containing {@code [a, b, c, d, e]} with a partition size of 3 621090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * yields {@code [[a, b, c], [d, e, null]]} -- an outer iterator containing 622090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * two inner lists of three elements each, all in the original order. 623090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 624090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned lists implement {@link java.util.RandomAccess}. 625090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 626090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param iterator the iterator to return a partitioned view of 627090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param size the desired size of each partition 628090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @return an iterator of immutable lists containing the elements of {@code 629090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterator} divided into partitions (the final iterable may have 630090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * trailing null elements) 631090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws IllegalArgumentException if {@code size} is nonpositive 632090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 6337dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> UnmodifiableIterator<List<T>> paddedPartition(Iterator<T> iterator, int size) { 634090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return partitionImpl(iterator, size, true); 635090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 636090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 6377dd252788645e940eada959bdde927426e2531c9Paul Duffin private static <T> UnmodifiableIterator<List<T>> partitionImpl(final Iterator<T> iterator, 6387dd252788645e940eada959bdde927426e2531c9Paul Duffin final int size, final boolean pad) { 639090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(iterator); 640090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkArgument(size > 0); 641090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new UnmodifiableIterator<List<T>>() { 6427dd252788645e940eada959bdde927426e2531c9Paul Duffin 643090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasNext() { 644090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.hasNext(); 645090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 6467dd252788645e940eada959bdde927426e2531c9Paul Duffin 647090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public List<T> next() { 648090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!hasNext()) { 649090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson throw new NoSuchElementException(); 650090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 651090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Object[] array = new Object[size]; 652090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson int count = 0; 653090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson for (; count < size && iterator.hasNext(); count++) { 654090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson array[count] = iterator.next(); 655090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 6561d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert for (int i = count; i < size; i++) { 6571d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert array[i] = null; // for GWT 6581d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 659090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 6607dd252788645e940eada959bdde927426e2531c9Paul Duffin @SuppressWarnings("unchecked") 6617dd252788645e940eada959bdde927426e2531c9Paul Duffin // we only put Ts in it 6627dd252788645e940eada959bdde927426e2531c9Paul Duffin List<T> list = Collections.unmodifiableList((List<T>) Arrays.asList(array)); 6631d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return (pad || count == size) ? list : list.subList(0, count); 664090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 665090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 666090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 667090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 668090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 669090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns the elements of {@code unfiltered} that satisfy a predicate. 670090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 6717dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> UnmodifiableIterator<T> filter(final Iterator<T> unfiltered, 6727dd252788645e940eada959bdde927426e2531c9Paul Duffin final Predicate<? super T> predicate) { 673090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(unfiltered); 674090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(predicate); 675090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new AbstractIterator<T>() { 6767dd252788645e940eada959bdde927426e2531c9Paul Duffin @Override 6777dd252788645e940eada959bdde927426e2531c9Paul Duffin protected T computeNext() { 678090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (unfiltered.hasNext()) { 679090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson T element = unfiltered.next(); 680090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (predicate.apply(element)) { 681090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return element; 682090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 683090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 684090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return endOfData(); 685090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 686090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 687090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 688090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 689090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 690090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns all instances of class {@code type} in {@code unfiltered}. The 691090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * returned iterator has elements whose class is {@code type} or a subclass of 692090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code type}. 693090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 694090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param unfiltered an iterator containing objects of any type 695090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param type the type of elements desired 696090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @return an unmodifiable iterator containing all elements of the original 697090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterator that were of the requested type 698090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 6997dd252788645e940eada959bdde927426e2531c9Paul Duffin @SuppressWarnings("unchecked") 7007dd252788645e940eada959bdde927426e2531c9Paul Duffin // can cast to <T> because non-Ts are removed 701090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @GwtIncompatible("Class.isInstance") 7027dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> UnmodifiableIterator<T> filter(Iterator<?> unfiltered, Class<T> type) { 7037dd252788645e940eada959bdde927426e2531c9Paul Duffin return (UnmodifiableIterator<T>) filter(unfiltered, Predicates.instanceOf(type)); 704090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 705090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 706090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 707090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns {@code true} if one or more elements returned by {@code iterator} 708090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * satisfy the given predicate. 709090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 7107dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> boolean any(Iterator<T> iterator, Predicate<? super T> predicate) { 711090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(predicate); 712090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (iterator.hasNext()) { 713090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson T element = iterator.next(); 714090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (predicate.apply(element)) { 715090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return true; 716090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 717090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 718090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return false; 719090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 720090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 721090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 722090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns {@code true} if every element returned by {@code iterator} 723090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * satisfies the given predicate. If {@code iterator} is empty, {@code true} 724090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * is returned. 725090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 7267dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> boolean all(Iterator<T> iterator, Predicate<? super T> predicate) { 727090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(predicate); 728090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (iterator.hasNext()) { 729090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson T element = iterator.next(); 730090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!predicate.apply(element)) { 731090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return false; 732090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 733090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 734090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return true; 735090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 736090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 737090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 738090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns the first element in {@code iterator} that satisfies the given 7391d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * predicate; use this method only when such an element is known to exist. If 7401d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * no such element is found, the iterator will be left exhausted: its {@code 7411d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * hasNext()} method will return {@code false}. If it is possible that 7427dd252788645e940eada959bdde927426e2531c9Paul Duffin * <i>no</i> element will match, use {@link #tryFind} or {@link 7437dd252788645e940eada959bdde927426e2531c9Paul Duffin * #find(Iterator, Predicate, Object)} instead. 744090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 745090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws NoSuchElementException if no element in {@code iterator} matches 746090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * the given predicate 747090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 7487dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> T find(Iterator<T> iterator, Predicate<? super T> predicate) { 749090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return filter(iterator, predicate).next(); 750090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 751090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 752090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 7531d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Returns the first element in {@code iterator} that satisfies the given 7541d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * predicate. If no such element is found, {@code defaultValue} will be 7551d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * returned from this method and the iterator will be left exhausted: its 7561d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code hasNext()} method will return {@code false}. Note that this can 7571d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * usually be handled more naturally using {@code 7581d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * tryFind(iterator, predicate).or(defaultValue)}. 7591d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 7601d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 7.0 7611d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 7627dd252788645e940eada959bdde927426e2531c9Paul Duffin @Nullable 7637dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> T find(Iterator<? extends T> iterator, Predicate<? super T> predicate, 7641d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Nullable T defaultValue) { 7657dd252788645e940eada959bdde927426e2531c9Paul Duffin UnmodifiableIterator<? extends T> filteredIterator = filter(iterator, predicate); 7661d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return filteredIterator.hasNext() ? filteredIterator.next() : defaultValue; 7671d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 7681d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 7691d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 7701d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Returns an {@link Optional} containing the first element in {@code 7711d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * iterator} that satisfies the given predicate, if such an element exists. If 7721d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * no such element is found, an empty {@link Optional} will be returned from 7731d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * this method and the the iterator will be left exhausted: its {@code 7741d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * hasNext()} method will return {@code false}. 7751d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 7761d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p><b>Warning:</b> avoid using a {@code predicate} that matches {@code 7771d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * null}. If {@code null} is matched in {@code iterator}, a 7781d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * NullPointerException will be thrown. 7791d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 7801d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 11.0 7811d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 7827dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> Optional<T> tryFind(Iterator<T> iterator, Predicate<? super T> predicate) { 7831d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert UnmodifiableIterator<T> filteredIterator = filter(iterator, predicate); 7847dd252788645e940eada959bdde927426e2531c9Paul Duffin return filteredIterator.hasNext() ? Optional.of(filteredIterator.next()) : Optional 7857dd252788645e940eada959bdde927426e2531c9Paul Duffin .<T> absent(); 7861d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 7871d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 7881d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 789bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * Returns the index in {@code iterator} of the first element that satisfies 790bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * the provided {@code predicate}, or {@code -1} if the Iterator has no such 791bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * elements. 792bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * 793bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * <p>More formally, returns the lowest index {@code i} such that 7941d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code predicate.apply(Iterators.get(iterator, i))} returns {@code true}, 7951d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * or {@code -1} if there is no such index. 796bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * 797bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * <p>If -1 is returned, the iterator will be left exhausted: its 798bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * {@code hasNext()} method will return {@code false}. Otherwise, 799bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * the iterator will be set to the element which satisfies the 800bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * {@code predicate}. 801bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * 8021d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 2.0 803bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor */ 8047dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> int indexOf(Iterator<T> iterator, Predicate<? super T> predicate) { 8051d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkNotNull(predicate, "predicate"); 806bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor int i = 0; 807bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor while (iterator.hasNext()) { 808bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor T current = iterator.next(); 809bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor if (predicate.apply(current)) { 810bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor return i; 811bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor } 812bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor i++; 813bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor } 814bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor return -1; 815bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor } 816bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor 817bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor /** 818090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns an iterator that applies {@code function} to each element of {@code 819090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * fromIterator}. 820090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 821090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned iterator supports {@code remove()} if the provided iterator 822090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * does. After a successful {@code remove()} call, {@code fromIterator} no 823090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * longer contains the corresponding element. 824090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 825090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <F, T> Iterator<T> transform(final Iterator<F> fromIterator, 826090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson final Function<? super F, ? extends T> function) { 827090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(function); 8287dd252788645e940eada959bdde927426e2531c9Paul Duffin return new TransformedIterator<F, T>(fromIterator) { 8297dd252788645e940eada959bdde927426e2531c9Paul Duffin 8301d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 8317dd252788645e940eada959bdde927426e2531c9Paul Duffin T transform(F from) { 832090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return function.apply(from); 833090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 834090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 835090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 836090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 837090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 8381d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Advances {@code iterator} {@code position + 1} times, returning the 8391d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * element at the {@code position}th position. 840090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 841090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param position position of the element to return 842090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @return the element at the specified position in {@code iterator} 843090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws IndexOutOfBoundsException if {@code position} is negative or 844090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * greater than or equal to the number of elements remaining in 845090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code iterator} 846090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 847090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> T get(Iterator<T> iterator, int position) { 8481d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkNonnegative(position); 849090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 850090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson int skipped = 0; 851090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (iterator.hasNext()) { 852090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson T t = iterator.next(); 853090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (skipped++ == position) { 854090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return t; 855090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 856090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 857090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 858090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson throw new IndexOutOfBoundsException("position (" + position 8597dd252788645e940eada959bdde927426e2531c9Paul Duffin + ") must be less than the number of elements that remained (" + skipped + ")"); 860090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 861090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 8621d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert private static void checkNonnegative(int position) { 8631d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert if (position < 0) { 8647dd252788645e940eada959bdde927426e2531c9Paul Duffin throw new IndexOutOfBoundsException("position (" + position + ") must not be negative"); 8651d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 8661d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 8671d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 8681d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 8691d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Advances {@code iterator} {@code position + 1} times, returning the 8701d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * element at the {@code position}th position or {@code defaultValue} 8711d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * otherwise. 8721d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 8731d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @param position position of the element to return 8741d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @param defaultValue the default value to return if the iterator is empty 8751d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * or if {@code position} is greater than the number of elements 8761d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * remaining in {@code iterator} 8771d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @return the element at the specified position in {@code iterator} or 8781d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code defaultValue} if {@code iterator} produces fewer than 8791d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code position + 1} elements. 8801d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @throws IndexOutOfBoundsException if {@code position} is negative 8811d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 4.0 8821d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 8837dd252788645e940eada959bdde927426e2531c9Paul Duffin @Nullable 8847dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> T get(Iterator<? extends T> iterator, int position, @Nullable T defaultValue) { 8851d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkNonnegative(position); 8861d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 8871d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert try { 8881d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return get(iterator, position); 8891d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } catch (IndexOutOfBoundsException e) { 8901d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return defaultValue; 8911d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 8921d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 8931d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 8941d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 8951d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Returns the next element in {@code iterator} or {@code defaultValue} if 8961d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * the iterator is empty. The {@link Iterables} analog to this method is 8971d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@link Iterables#getFirst}. 8981d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 8991d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @param defaultValue the default value to return if the iterator is empty 9001d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @return the next element of {@code iterator} or the default value 9011d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 7.0 9021d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 9037dd252788645e940eada959bdde927426e2531c9Paul Duffin @Nullable 9047dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> T getNext(Iterator<? extends T> iterator, @Nullable T defaultValue) { 9051d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return iterator.hasNext() ? iterator.next() : defaultValue; 9061d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 9071d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 908090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 909090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Advances {@code iterator} to the end, returning the last element. 910090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 911090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @return the last element of {@code iterator} 9121d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @throws NoSuchElementException if the iterator is empty 913090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 914090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> T getLast(Iterator<T> iterator) { 915090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (true) { 916090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson T current = iterator.next(); 917090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!iterator.hasNext()) { 918090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return current; 919090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 920090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 921090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 922090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 923bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor /** 9241d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Advances {@code iterator} to the end, returning the last element or 9251d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code defaultValue} if the iterator is empty. 9261d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 9271d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @param defaultValue the default value to return if the iterator is empty 9281d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @return the last element of {@code iterator} 9291d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 3.0 9301d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 9317dd252788645e940eada959bdde927426e2531c9Paul Duffin @Nullable 9327dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> T getLast(Iterator<? extends T> iterator, @Nullable T defaultValue) { 9331d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return iterator.hasNext() ? getLast(iterator) : defaultValue; 9341d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 9351d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 9361d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 9377dd252788645e940eada959bdde927426e2531c9Paul Duffin * Calls {@code next()} on {@code iterator}, either {@code numberToAdvance} times 9381d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * or until {@code hasNext()} returns {@code false}, whichever comes first. 9391d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 9407dd252788645e940eada959bdde927426e2531c9Paul Duffin * @return the number of elements the iterator was advanced 9417dd252788645e940eada959bdde927426e2531c9Paul Duffin * @since 13.0 (since 3.0 as {@code Iterators.skip}) 9421d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 9437dd252788645e940eada959bdde927426e2531c9Paul Duffin public static int advance(Iterator<?> iterator, int numberToAdvance) { 9441d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkNotNull(iterator); 9457dd252788645e940eada959bdde927426e2531c9Paul Duffin checkArgument(numberToAdvance >= 0, "number to advance cannot be negative"); 9461d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 9471d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert int i; 9487dd252788645e940eada959bdde927426e2531c9Paul Duffin for (i = 0; i < numberToAdvance && iterator.hasNext(); i++) { 9491d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert iterator.next(); 9501d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 9511d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return i; 9521d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 9531d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 9541d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 9551d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Creates an iterator returning the first {@code limitSize} elements of the 9561d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * given iterator. If the original iterator does not contain that many 9571d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * elements, the returned iterator will have the same behavior as the original 9581d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * iterator. The returned iterator supports {@code remove()} if the original 9591d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * iterator does. 9601d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 9611d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @param iterator the iterator to limit 9621d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @param limitSize the maximum number of elements in the returned iterator 9631d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @throws IllegalArgumentException if {@code limitSize} is negative 9641d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 3.0 9651d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 9667dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> Iterator<T> limit(final Iterator<T> iterator, final int limitSize) { 9671d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkNotNull(iterator); 9681d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkArgument(limitSize >= 0, "limit is negative"); 9691d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return new Iterator<T>() { 9701d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert private int count; 9711d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 9721d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public boolean hasNext() { 9731d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return count < limitSize && iterator.hasNext(); 9741d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 9751d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 9761d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public T next() { 9771d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert if (!hasNext()) { 9781d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert throw new NoSuchElementException(); 9791d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 9801d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert count++; 9811d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return iterator.next(); 9821d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 9831d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 9841d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public void remove() { 9851d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert iterator.remove(); 9861d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 9871d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert }; 9881d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 9891d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 9901d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 991bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * Returns a view of the supplied {@code iterator} that removes each element 992bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * from the supplied {@code iterator} as it is returned. 993bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * 994bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * <p>The provided iterator must support {@link Iterator#remove()} or 995bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * else the returned iterator will fail on the first call to {@code 996bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * next}. 997bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * 998bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * @param iterator the iterator to remove and return elements from 999bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * @return an iterator that removes and returns elements from the 1000bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * supplied iterator 10011d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 2.0 1002bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor */ 1003bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor public static <T> Iterator<T> consumingIterator(final Iterator<T> iterator) { 1004bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor checkNotNull(iterator); 1005bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor return new UnmodifiableIterator<T>() { 10067dd252788645e940eada959bdde927426e2531c9Paul Duffin 1007bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor public boolean hasNext() { 1008bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor return iterator.hasNext(); 1009bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor } 1010bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor 1011bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor public T next() { 1012bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor T next = iterator.next(); 1013bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor iterator.remove(); 1014bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor return next; 1015bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor } 1016bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor }; 1017bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor } 1018bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor 10197dd252788645e940eada959bdde927426e2531c9Paul Duffin /** 10207dd252788645e940eada959bdde927426e2531c9Paul Duffin * Deletes and returns the next value from the iterator, or returns 10217dd252788645e940eada959bdde927426e2531c9Paul Duffin * {@code defaultValue} if there is no such value. 10227dd252788645e940eada959bdde927426e2531c9Paul Duffin */ 10237dd252788645e940eada959bdde927426e2531c9Paul Duffin @Nullable 10247dd252788645e940eada959bdde927426e2531c9Paul Duffin static <T> T pollNext(Iterator<T> iterator) { 10257dd252788645e940eada959bdde927426e2531c9Paul Duffin if (iterator.hasNext()) { 10267dd252788645e940eada959bdde927426e2531c9Paul Duffin T result = iterator.next(); 10277dd252788645e940eada959bdde927426e2531c9Paul Duffin iterator.remove(); 10287dd252788645e940eada959bdde927426e2531c9Paul Duffin return result; 10297dd252788645e940eada959bdde927426e2531c9Paul Duffin } else { 10307dd252788645e940eada959bdde927426e2531c9Paul Duffin return null; 10317dd252788645e940eada959bdde927426e2531c9Paul Duffin } 10327dd252788645e940eada959bdde927426e2531c9Paul Duffin } 10337dd252788645e940eada959bdde927426e2531c9Paul Duffin 1034090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // Methods only in Iterators, not in Iterables 1035090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1036090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 10371d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Clears the iterator using its remove method. 10381d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 10391d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert static void clear(Iterator<?> iterator) { 10401d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkNotNull(iterator); 10411d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert while (iterator.hasNext()) { 10421d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert iterator.next(); 10431d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert iterator.remove(); 10441d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 10451d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 10461d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 10471d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 1048090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns an iterator containing the elements of {@code array} in order. The 1049090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * returned iterator is a view of the array; subsequent changes to the array 1050090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * will be reflected in the iterator. 1051090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1052090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p><b>Note:</b> It is often preferable to represent your data using a 1053090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * collection type, for example using {@link Arrays#asList(Object[])}, making 1054090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * this method unnecessary. 1055090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1056090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The {@code Iterable} equivalent of this method is either {@link 10571d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Arrays#asList(Object[])}, {@link ImmutableList#copyOf(Object[])}}, 10581d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * or {@link ImmutableList#of}. 1059090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 1060090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> UnmodifiableIterator<T> forArray(final T... array) { 10611d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert // TODO(kevinb): compare performance with Arrays.asList(array).iterator(). 10627dd252788645e940eada959bdde927426e2531c9Paul Duffin checkNotNull(array); // eager for GWT. 10631d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return new AbstractIndexedListIterator<T>(array.length) { 10647dd252788645e940eada959bdde927426e2531c9Paul Duffin @Override 10657dd252788645e940eada959bdde927426e2531c9Paul Duffin protected T get(int index) { 10661d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return array[index]; 1067090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1068090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 1069090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1070090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1071090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 10727dd252788645e940eada959bdde927426e2531c9Paul Duffin * Returns a list iterator containing the elements in the specified range of 10737dd252788645e940eada959bdde927426e2531c9Paul Duffin * {@code array} in order, starting at the specified index. 1074090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1075090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The {@code Iterable} equivalent of this method is {@code 10767dd252788645e940eada959bdde927426e2531c9Paul Duffin * Arrays.asList(array).subList(offset, offset + length).listIterator(index)}. 1077090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 10787dd252788645e940eada959bdde927426e2531c9Paul Duffin static <T> UnmodifiableListIterator<T> forArray(final T[] array, final int offset, int length, 10797dd252788645e940eada959bdde927426e2531c9Paul Duffin int index) { 1080090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkArgument(length >= 0); 10811d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert int end = offset + length; 1082090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1083090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // Technically we should give a slightly more descriptive error on overflow 1084090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Preconditions.checkPositionIndexes(offset, end, array.length); 1085090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 10861d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /* 10871d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * We can't use call the two-arg constructor with arguments (offset, end) 10881d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * because the returned Iterator is a ListIterator that may be moved back 10891d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * past the beginning of the iteration. 10901d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 10917dd252788645e940eada959bdde927426e2531c9Paul Duffin return new AbstractIndexedListIterator<T>(length, index) { 10927dd252788645e940eada959bdde927426e2531c9Paul Duffin @Override 10937dd252788645e940eada959bdde927426e2531c9Paul Duffin protected T get(int index) { 10941d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return array[offset + index]; 1095090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1096090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 1097090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1098090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1099090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 1100090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns an iterator containing only {@code value}. 1101090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1102090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The {@link Iterable} equivalent of this method is {@link 1103090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Collections#singleton}. 1104090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 11057dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> UnmodifiableIterator<T> singletonIterator(@Nullable final T value) { 1106090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new UnmodifiableIterator<T>() { 1107090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson boolean done; 11087dd252788645e940eada959bdde927426e2531c9Paul Duffin 1109090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasNext() { 1110090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return !done; 1111090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 11127dd252788645e940eada959bdde927426e2531c9Paul Duffin 1113090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public T next() { 1114090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (done) { 1115090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson throw new NoSuchElementException(); 1116090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1117090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson done = true; 1118090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return value; 1119090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1120090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 1121090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1122090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1123090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 1124090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Adapts an {@code Enumeration} to the {@code Iterator} interface. 1125090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1126090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>This method has no equivalent in {@link Iterables} because viewing an 1127090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code Enumeration} as an {@code Iterable} is impossible. However, the 1128090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * contents can be <i>copied</i> into a collection using {@link 1129090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Collections#list}. 1130090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 11317dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> UnmodifiableIterator<T> forEnumeration(final Enumeration<T> enumeration) { 1132090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(enumeration); 1133090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new UnmodifiableIterator<T>() { 11347dd252788645e940eada959bdde927426e2531c9Paul Duffin 1135090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasNext() { 1136090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return enumeration.hasMoreElements(); 1137090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 11387dd252788645e940eada959bdde927426e2531c9Paul Duffin 1139090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public T next() { 1140090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return enumeration.nextElement(); 1141090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1142090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 1143090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1144090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1145090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 1146090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Adapts an {@code Iterator} to the {@code Enumeration} interface. 1147090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1148090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The {@code Iterable} equivalent of this method is either {@link 1149090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Collections#enumeration} (if you have a {@link Collection}), or 1150090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code Iterators.asEnumeration(collection.iterator())}. 1151090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 1152090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> Enumeration<T> asEnumeration(final Iterator<T> iterator) { 1153090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(iterator); 1154090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new Enumeration<T>() { 11557dd252788645e940eada959bdde927426e2531c9Paul Duffin 1156090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasMoreElements() { 1157090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.hasNext(); 1158090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 11597dd252788645e940eada959bdde927426e2531c9Paul Duffin 1160090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public T nextElement() { 1161090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.next(); 1162090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1163090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 1164090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1165090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1166090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 1167090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Implementation of PeekingIterator that avoids peeking unless necessary. 1168090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 1169090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson private static class PeekingImpl<E> implements PeekingIterator<E> { 1170090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1171090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson private final Iterator<? extends E> iterator; 1172090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson private boolean hasPeeked; 1173090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson private E peekedElement; 1174090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1175090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public PeekingImpl(Iterator<? extends E> iterator) { 1176090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson this.iterator = checkNotNull(iterator); 1177090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1178090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1179090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasNext() { 1180090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return hasPeeked || iterator.hasNext(); 1181090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1182090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1183090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public E next() { 1184090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!hasPeeked) { 1185090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.next(); 1186090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1187090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson E result = peekedElement; 1188090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson hasPeeked = false; 1189090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson peekedElement = null; 1190090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return result; 1191090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1192090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1193090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public void remove() { 1194090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkState(!hasPeeked, "Can't remove after you've peeked at next"); 1195090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson iterator.remove(); 1196090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1197090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1198090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public E peek() { 1199090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!hasPeeked) { 1200090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson peekedElement = iterator.next(); 1201090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson hasPeeked = true; 1202090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1203090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return peekedElement; 1204090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1205090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1206090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1207090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 1208090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns a {@code PeekingIterator} backed by the given iterator. 1209090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1210090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>Calls to the {@code peek} method with no intervening calls to {@code 1211090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * next} do not affect the iteration, and hence return the same object each 1212090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * time. A subsequent call to {@code next} is guaranteed to return the same 1213090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * object again. For example: <pre> {@code 1214090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1215090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * PeekingIterator<String> peekingIterator = 1216090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Iterators.peekingIterator(Iterators.forArray("a", "b")); 1217090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * String a1 = peekingIterator.peek(); // returns "a" 1218090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * String a2 = peekingIterator.peek(); // also returns "a" 1219090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * String a3 = peekingIterator.next(); // also returns "a"}</pre> 1220090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1221090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Any structural changes to the underlying iteration (aside from those 1222090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * performed by the iterator's own {@link PeekingIterator#remove()} method) 1223090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * will leave the iterator in an undefined state. 1224090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1225090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned iterator does not support removal after peeking, as 1226090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * explained by {@link PeekingIterator#remove()}. 1227090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1228090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>Note: If the given iterator is already a {@code PeekingIterator}, 1229090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * it <i>might</i> be returned to the caller, although this is neither 1230090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * guaranteed to occur nor required to be consistent. For example, this 1231090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * method <i>might</i> choose to pass through recognized implementations of 1232090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code PeekingIterator} when the behavior of the implementation is 1233090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * known to meet the contract guaranteed by this method. 1234090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1235090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>There is no {@link Iterable} equivalent to this method, so use this 1236090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * method to wrap each individual iterator as it is generated. 1237090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1238090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param iterator the backing iterator. The {@link PeekingIterator} assumes 1239090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * ownership of this iterator, so users should cease making direct calls 1240090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * to it after calling this method. 1241090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @return a peeking iterator backed by that iterator. Apart from the 1242090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * additional {@link PeekingIterator#peek()} method, this iterator behaves 1243090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * exactly the same as {@code iterator}. 1244090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 12457dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> PeekingIterator<T> peekingIterator(Iterator<? extends T> iterator) { 1246090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (iterator instanceof PeekingImpl) { 1247090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // Safe to cast <? extends T> to <T> because PeekingImpl only uses T 1248090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // covariantly (and cannot be subclassed to add non-covariant uses). 1249090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @SuppressWarnings("unchecked") 1250090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson PeekingImpl<T> peeking = (PeekingImpl<T>) iterator; 1251090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return peeking; 1252090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1253090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new PeekingImpl<T>(iterator); 1254090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 12551d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 12561d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 12571d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Simply returns its argument. 12581d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 12591d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @deprecated no need to use this 12601d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 10.0 12611d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 12627dd252788645e940eada959bdde927426e2531c9Paul Duffin @Deprecated 12637dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> PeekingIterator<T> peekingIterator(PeekingIterator<T> iterator) { 12641d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return checkNotNull(iterator); 12651d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 12661d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 12671d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 12681d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Returns an iterator over the merged contents of all given 12691d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code iterators}, traversing every element of the input iterators. 12701d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Equivalent entries will not be de-duplicated. 12711d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 12721d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p>Callers must ensure that the source {@code iterators} are in 12731d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * non-descending order as this method does not sort its input. 12741d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 12751d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p>For any equivalent elements across all {@code iterators}, it is 12761d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * undefined which element is returned first. 12771d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 12781d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 11.0 12791d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 12801d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Beta 12811d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public static <T> UnmodifiableIterator<T> mergeSorted( 12827dd252788645e940eada959bdde927426e2531c9Paul Duffin Iterable<? extends Iterator<? extends T>> iterators, Comparator<? super T> comparator) { 12831d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkNotNull(iterators, "iterators"); 12841d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkNotNull(comparator, "comparator"); 12851d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 12861d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return new MergingIterator<T>(iterators, comparator); 12871d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 12881d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 12891d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 12901d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * An iterator that performs a lazy N-way merge, calculating the next value 12911d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * each time the iterator is polled. This amortizes the sorting cost over the 12921d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * iteration and requires less memory than sorting all elements at once. 12931d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 12941d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p>Retrieving a single element takes approximately O(log(M)) time, where M 12951d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * is the number of iterators. (Retrieving all elements takes approximately 12961d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * O(N*log(M)) time, where N is the total number of elements.) 12971d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 12981d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert private static class MergingIterator<T> extends AbstractIterator<T> { 12991d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert final Queue<PeekingIterator<T>> queue; 13001d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert final Comparator<? super T> comparator; 13011d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 13021d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public MergingIterator(Iterable<? extends Iterator<? extends T>> iterators, 13031d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert Comparator<? super T> itemComparator) { 13041d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert this.comparator = itemComparator; 13051d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 13061d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert // A comparator that's used by the heap, allowing the heap 13071d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert // to be sorted based on the top of each iterator. 13087dd252788645e940eada959bdde927426e2531c9Paul Duffin Comparator<PeekingIterator<T>> heapComparator = new Comparator<PeekingIterator<T>>() { 13097dd252788645e940eada959bdde927426e2531c9Paul Duffin 13107dd252788645e940eada959bdde927426e2531c9Paul Duffin public int compare(PeekingIterator<T> o1, PeekingIterator<T> o2) { 13117dd252788645e940eada959bdde927426e2531c9Paul Duffin return comparator.compare(o1.peek(), o2.peek()); 13127dd252788645e940eada959bdde927426e2531c9Paul Duffin } 13137dd252788645e940eada959bdde927426e2531c9Paul Duffin }; 13141d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 13151d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert queue = new PriorityQueue<PeekingIterator<T>>(2, heapComparator); 13161d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 13171d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert for (Iterator<? extends T> iterator : iterators) { 13181d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert if (iterator.hasNext()) { 13191d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert queue.add(Iterators.peekingIterator(iterator)); 13201d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 13211d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 13221d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 13231d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 13241d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 13251d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert protected T computeNext() { 13261d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert if (queue.isEmpty()) { 13271d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return endOfData(); 13281d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 13291d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 13301d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert PeekingIterator<T> nextIter = queue.poll(); 13311d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert T next = nextIter.next(); 13321d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 13331d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert if (nextIter.hasNext()) { 13341d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert queue.add(nextIter); 13351d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 13361d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 13371d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return next; 13381d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 13391d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 13407dd252788645e940eada959bdde927426e2531c9Paul Duffin 13417dd252788645e940eada959bdde927426e2531c9Paul Duffin /** 13427dd252788645e940eada959bdde927426e2531c9Paul Duffin * Precondition tester for {@code Iterator.remove()} that throws an exception with a consistent 13437dd252788645e940eada959bdde927426e2531c9Paul Duffin * error message. 13447dd252788645e940eada959bdde927426e2531c9Paul Duffin */ 13457dd252788645e940eada959bdde927426e2531c9Paul Duffin static void checkRemove(boolean canRemove) { 13467dd252788645e940eada959bdde927426e2531c9Paul Duffin checkState(canRemove, "no calls to next() since the last call to remove()"); 13477dd252788645e940eada959bdde927426e2531c9Paul Duffin } 13487dd252788645e940eada959bdde927426e2531c9Paul Duffin 13497dd252788645e940eada959bdde927426e2531c9Paul Duffin /** 13507dd252788645e940eada959bdde927426e2531c9Paul Duffin * Used to avoid http://bugs.sun.com/view_bug.do?bug_id=6558557 13517dd252788645e940eada959bdde927426e2531c9Paul Duffin */ 13527dd252788645e940eada959bdde927426e2531c9Paul Duffin static <T> ListIterator<T> cast(Iterator<T> iterator) { 13537dd252788645e940eada959bdde927426e2531c9Paul Duffin return (ListIterator<T>) iterator; 13547dd252788645e940eada959bdde927426e2531c9Paul Duffin } 1355090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson} 1356