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; 220888a09821a98ac0680fad765217302858e70fa4Paul Duffinimport static com.google.common.base.Predicates.equalTo; 230888a09821a98ac0680fad765217302858e70fa4Paul Duffinimport static com.google.common.base.Predicates.in; 240888a09821a98ac0680fad765217302858e70fa4Paul Duffinimport static com.google.common.base.Predicates.instanceOf; 250888a09821a98ac0680fad765217302858e70fa4Paul Duffinimport static com.google.common.base.Predicates.not; 260888a09821a98ac0680fad765217302858e70fa4Paul Duffinimport static com.google.common.collect.CollectPreconditions.checkRemove; 271d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 281d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport com.google.common.annotations.Beta; 29090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport com.google.common.annotations.GwtCompatible; 30090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport com.google.common.annotations.GwtIncompatible; 31090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport com.google.common.base.Function; 32090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport com.google.common.base.Objects; 331d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport com.google.common.base.Optional; 34090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport com.google.common.base.Preconditions; 35090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport com.google.common.base.Predicate; 36090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 37090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport java.util.Arrays; 38090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport java.util.Collection; 39090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport java.util.Collections; 401d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport java.util.Comparator; 41090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport java.util.Enumeration; 42090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport java.util.Iterator; 43090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport java.util.List; 447dd252788645e940eada959bdde927426e2531c9Paul Duffinimport java.util.ListIterator; 45090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport java.util.NoSuchElementException; 461d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport java.util.PriorityQueue; 471d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport java.util.Queue; 48090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 49090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport javax.annotation.Nullable; 50090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 51090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson/** 52090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * This class contains static utility methods that operate on or return objects 53090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * of type {@link Iterator}. Except as noted, each method has a corresponding 54090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@link Iterable}-based method in the {@link Iterables} class. 55090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 561d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p><i>Performance notes:</i> Unless otherwise noted, all of the iterators 571d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * produced in this class are <i>lazy</i>, which means that they only advance 581d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * the backing iteration when absolutely necessary. 591d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 607dd252788645e940eada959bdde927426e2531c9Paul Duffin * <p>See the Guava User Guide section on <a href= 617dd252788645e940eada959bdde927426e2531c9Paul Duffin * "http://code.google.com/p/guava-libraries/wiki/CollectionUtilitiesExplained#Iterables"> 627dd252788645e940eada959bdde927426e2531c9Paul Duffin * {@code Iterators}</a>. 637dd252788645e940eada959bdde927426e2531c9Paul Duffin * 64090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @author Kevin Bourrillion 65090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @author Jared Levy 661d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 2.0 (imported from Google Collections Library) 67090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 681d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert@GwtCompatible(emulated = true) 69090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonpublic final class Iterators { 70090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson private Iterators() {} 71090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 720888a09821a98ac0680fad765217302858e70fa4Paul Duffin static final UnmodifiableListIterator<Object> EMPTY_LIST_ITERATOR 730888a09821a98ac0680fad765217302858e70fa4Paul Duffin = new UnmodifiableListIterator<Object>() { 740888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 750888a09821a98ac0680fad765217302858e70fa4Paul Duffin public boolean hasNext() { 760888a09821a98ac0680fad765217302858e70fa4Paul Duffin return false; 770888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 780888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 790888a09821a98ac0680fad765217302858e70fa4Paul Duffin public Object next() { 800888a09821a98ac0680fad765217302858e70fa4Paul Duffin throw new NoSuchElementException(); 810888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 820888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 830888a09821a98ac0680fad765217302858e70fa4Paul Duffin public boolean hasPrevious() { 840888a09821a98ac0680fad765217302858e70fa4Paul Duffin return false; 850888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 860888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 870888a09821a98ac0680fad765217302858e70fa4Paul Duffin public Object previous() { 880888a09821a98ac0680fad765217302858e70fa4Paul Duffin throw new NoSuchElementException(); 890888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 900888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 910888a09821a98ac0680fad765217302858e70fa4Paul Duffin public int nextIndex() { 920888a09821a98ac0680fad765217302858e70fa4Paul Duffin return 0; 930888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 940888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 950888a09821a98ac0680fad765217302858e70fa4Paul Duffin public int previousIndex() { 960888a09821a98ac0680fad765217302858e70fa4Paul Duffin return -1; 970888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 980888a09821a98ac0680fad765217302858e70fa4Paul Duffin }; 997dd252788645e940eada959bdde927426e2531c9Paul Duffin 1007dd252788645e940eada959bdde927426e2531c9Paul Duffin /** 1017dd252788645e940eada959bdde927426e2531c9Paul Duffin * Returns the empty iterator. 1027dd252788645e940eada959bdde927426e2531c9Paul Duffin * 1037dd252788645e940eada959bdde927426e2531c9Paul Duffin * <p>The {@link Iterable} equivalent of this method is {@link 1047dd252788645e940eada959bdde927426e2531c9Paul Duffin * ImmutableSet#of()}. 1053ecfa412eddc4b084663f38d562537b86b9734d5Paul Duffin * 1063ecfa412eddc4b084663f38d562537b86b9734d5Paul Duffin * @deprecated Use {@code ImmutableSet.<T>of().iterator()} instead; or for 1073ecfa412eddc4b084663f38d562537b86b9734d5Paul Duffin * Java 7 or later, {@link Collections#emptyIterator}. This method is 1083ecfa412eddc4b084663f38d562537b86b9734d5Paul Duffin * scheduled for removal in May 2016. 1097dd252788645e940eada959bdde927426e2531c9Paul Duffin */ 1103ecfa412eddc4b084663f38d562537b86b9734d5Paul Duffin @Deprecated 1117dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> UnmodifiableIterator<T> emptyIterator() { 1127dd252788645e940eada959bdde927426e2531c9Paul Duffin return emptyListIterator(); 1137dd252788645e940eada959bdde927426e2531c9Paul Duffin } 114090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 115090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 116090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns the empty iterator. 117090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 118090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The {@link Iterable} equivalent of this method is {@link 1191d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * ImmutableSet#of()}. 120090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 121090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // Casting to any type is safe since there are no actual elements. 122090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @SuppressWarnings("unchecked") 1237dd252788645e940eada959bdde927426e2531c9Paul Duffin static <T> UnmodifiableListIterator<T> emptyListIterator() { 1247dd252788645e940eada959bdde927426e2531c9Paul Duffin return (UnmodifiableListIterator<T>) EMPTY_LIST_ITERATOR; 125090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 126090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1270888a09821a98ac0680fad765217302858e70fa4Paul Duffin private static final Iterator<Object> EMPTY_MODIFIABLE_ITERATOR = 1280888a09821a98ac0680fad765217302858e70fa4Paul Duffin new Iterator<Object>() { 1290888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override public boolean hasNext() { 1300888a09821a98ac0680fad765217302858e70fa4Paul Duffin return false; 1310888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 132090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1330888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override public Object next() { 1340888a09821a98ac0680fad765217302858e70fa4Paul Duffin throw new NoSuchElementException(); 1350888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 136090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1370888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override public void remove() { 1380888a09821a98ac0680fad765217302858e70fa4Paul Duffin checkRemove(false); 1390888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 1400888a09821a98ac0680fad765217302858e70fa4Paul Duffin }; 141090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 142090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 143090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns the empty {@code Iterator} that throws 144090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@link IllegalStateException} instead of 145090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@link UnsupportedOperationException} on a call to 146090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@link Iterator#remove()}. 147090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 148090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // Casting to any type is safe since there are no actual elements. 149090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @SuppressWarnings("unchecked") 150090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson static <T> Iterator<T> emptyModifiableIterator() { 151090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return (Iterator<T>) EMPTY_MODIFIABLE_ITERATOR; 152090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 153090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 154090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** Returns an unmodifiable view of {@code iterator}. */ 1550888a09821a98ac0680fad765217302858e70fa4Paul Duffin public static <T> UnmodifiableIterator<T> unmodifiableIterator( 1560888a09821a98ac0680fad765217302858e70fa4Paul Duffin final Iterator<T> iterator) { 157090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(iterator); 1581d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert if (iterator instanceof UnmodifiableIterator) { 1591d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return (UnmodifiableIterator<T>) iterator; 1601d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 161090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new UnmodifiableIterator<T>() { 1620888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 163090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasNext() { 164090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.hasNext(); 165090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1660888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 167090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public T next() { 168090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.next(); 169090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 170090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 171090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 172090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 173090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 1741d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Simply returns its argument. 1751d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 1761d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @deprecated no need to use this 1771d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 10.0 1781d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 1790888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Deprecated public static <T> UnmodifiableIterator<T> unmodifiableIterator( 1800888a09821a98ac0680fad765217302858e70fa4Paul Duffin UnmodifiableIterator<T> iterator) { 1811d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return checkNotNull(iterator); 1821d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 1831d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 1841d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 185090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns the number of elements remaining in {@code iterator}. The iterator 186090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * will be left exhausted: its {@code hasNext()} method will return 187090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code false}. 188090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 189090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static int size(Iterator<?> iterator) { 190090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson int count = 0; 191090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (iterator.hasNext()) { 192090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson iterator.next(); 193090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson count++; 194090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 195090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return count; 196090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 197090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 198090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 199090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns {@code true} if {@code iterator} contains {@code element}. 200090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 2017dd252788645e940eada959bdde927426e2531c9Paul Duffin public static boolean contains(Iterator<?> iterator, @Nullable Object element) { 2020888a09821a98ac0680fad765217302858e70fa4Paul Duffin return any(iterator, equalTo(element)); 203090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 204090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 205090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 206090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Traverses an iterator and removes every element that belongs to the 207090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * provided collection. The iterator will be left exhausted: its 208090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code hasNext()} method will return {@code false}. 209090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 210090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param removeFrom the iterator to (potentially) remove elements from 211090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param elementsToRemove the elements to remove 2121d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @return {@code true} if any element was removed from {@code iterator} 213090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 2140888a09821a98ac0680fad765217302858e70fa4Paul Duffin public static boolean removeAll( 2150888a09821a98ac0680fad765217302858e70fa4Paul Duffin Iterator<?> removeFrom, Collection<?> elementsToRemove) { 2160888a09821a98ac0680fad765217302858e70fa4Paul Duffin return removeIf(removeFrom, in(elementsToRemove)); 217090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 218090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 219090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 220090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Removes every element that satisfies the provided predicate from the 221090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterator. The iterator will be left exhausted: its {@code hasNext()} 222090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * method will return {@code false}. 223090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 224090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param removeFrom the iterator to (potentially) remove elements from 225090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param predicate a predicate that determines whether an element should 226090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * be removed 227090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @return {@code true} if any elements were removed from the iterator 2281d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 2.0 229090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 2300888a09821a98ac0680fad765217302858e70fa4Paul Duffin public static <T> boolean removeIf( 2310888a09821a98ac0680fad765217302858e70fa4Paul Duffin Iterator<T> removeFrom, Predicate<? super T> predicate) { 232090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(predicate); 233090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson boolean modified = false; 234090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (removeFrom.hasNext()) { 235090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (predicate.apply(removeFrom.next())) { 236090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson removeFrom.remove(); 237090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson modified = true; 238090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 239090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 240090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return modified; 241090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 242090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 243090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 244090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Traverses an iterator and removes every element that does not belong to the 245090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * provided collection. The iterator will be left exhausted: its 246090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code hasNext()} method will return {@code false}. 247090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 248090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param removeFrom the iterator to (potentially) remove elements from 249090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param elementsToRetain the elements to retain 2501d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @return {@code true} if any element was removed from {@code iterator} 251090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 2520888a09821a98ac0680fad765217302858e70fa4Paul Duffin public static boolean retainAll( 2530888a09821a98ac0680fad765217302858e70fa4Paul Duffin Iterator<?> removeFrom, Collection<?> elementsToRetain) { 2540888a09821a98ac0680fad765217302858e70fa4Paul Duffin return removeIf(removeFrom, not(in(elementsToRetain))); 255090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 256090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 257090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 258090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Determines whether two iterators contain equal elements in the same order. 259090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * More specifically, this method returns {@code true} if {@code iterator1} 260090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * and {@code iterator2} contain the same number of elements and every element 261090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * of {@code iterator1} is equal to the corresponding element of 262090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code iterator2}. 263090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 264090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>Note that this will modify the supplied iterators, since they will have 265090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * been advanced some number of elements forward. 266090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 2670888a09821a98ac0680fad765217302858e70fa4Paul Duffin public static boolean elementsEqual( 2680888a09821a98ac0680fad765217302858e70fa4Paul Duffin Iterator<?> iterator1, Iterator<?> iterator2) { 269090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (iterator1.hasNext()) { 270090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!iterator2.hasNext()) { 271090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return false; 272090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 273090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Object o1 = iterator1.next(); 274090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Object o2 = iterator2.next(); 275090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!Objects.equal(o1, o2)) { 276090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return false; 277090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 278090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 279090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return !iterator2.hasNext(); 280090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 281090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 282090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 283090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns a string representation of {@code iterator}, with the format 284090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code [e1, e2, ..., en]}. The iterator will be left exhausted: its 285090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code hasNext()} method will return {@code false}. 286090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 287090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static String toString(Iterator<?> iterator) { 2880888a09821a98ac0680fad765217302858e70fa4Paul Duffin return Collections2.STANDARD_JOINER 2890888a09821a98ac0680fad765217302858e70fa4Paul Duffin .appendTo(new StringBuilder().append('['), iterator) 2900888a09821a98ac0680fad765217302858e70fa4Paul Duffin .append(']') 2910888a09821a98ac0680fad765217302858e70fa4Paul Duffin .toString(); 292090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 293090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 294090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 295090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns the single element contained in {@code iterator}. 296090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 297090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws NoSuchElementException if the iterator is empty 298090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws IllegalArgumentException if the iterator contains multiple 299090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * elements. The state of the iterator is unspecified. 300090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 301090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> T getOnlyElement(Iterator<T> iterator) { 302090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson T first = iterator.next(); 303090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!iterator.hasNext()) { 304090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return first; 305090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 306090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 307090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson StringBuilder sb = new StringBuilder(); 308090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson sb.append("expected one element but was: <" + first); 309090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson for (int i = 0; i < 4 && iterator.hasNext(); i++) { 310090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson sb.append(", " + iterator.next()); 311090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 312090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (iterator.hasNext()) { 313090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson sb.append(", ..."); 314090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 3151d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert sb.append('>'); 316090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 317090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson throw new IllegalArgumentException(sb.toString()); 318090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 319090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 320090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 321090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns the single element contained in {@code iterator}, or {@code 322090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * defaultValue} if the iterator is empty. 323090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 324090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws IllegalArgumentException if the iterator contains multiple 325090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * elements. The state of the iterator is unspecified. 326090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 3277dd252788645e940eada959bdde927426e2531c9Paul Duffin @Nullable 3287dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> T getOnlyElement(Iterator<? extends T> iterator, @Nullable T defaultValue) { 329090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.hasNext() ? getOnlyElement(iterator) : defaultValue; 330090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 331090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 332090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 333090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Copies an iterator's elements into an array. The iterator will be left 334090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * exhausted: its {@code hasNext()} method will return {@code false}. 335090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 336090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param iterator the iterator to copy 337090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param type the type of the elements 338090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @return a newly-allocated array into which all the elements of the iterator 339090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * have been copied 340090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 3411d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @GwtIncompatible("Array.newInstance(Class, int)") 3420888a09821a98ac0680fad765217302858e70fa4Paul Duffin public static <T> T[] toArray( 3430888a09821a98ac0680fad765217302858e70fa4Paul Duffin Iterator<? extends T> iterator, Class<T> type) { 344090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson List<T> list = Lists.newArrayList(iterator); 345090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return Iterables.toArray(list, type); 346090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 347090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 348090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 349090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Adds all elements in {@code iterator} to {@code collection}. The iterator 350090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * will be left exhausted: its {@code hasNext()} method will return 351090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code false}. 352090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 353090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @return {@code true} if {@code collection} was modified as a result of this 354090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * operation 355090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 3560888a09821a98ac0680fad765217302858e70fa4Paul Duffin public static <T> boolean addAll( 3570888a09821a98ac0680fad765217302858e70fa4Paul Duffin Collection<T> addTo, Iterator<? extends T> iterator) { 358090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(addTo); 3590888a09821a98ac0680fad765217302858e70fa4Paul Duffin checkNotNull(iterator); 360090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson boolean wasModified = false; 361090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (iterator.hasNext()) { 362090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson wasModified |= addTo.add(iterator.next()); 363090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 364090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return wasModified; 365090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 366090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 367090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 368090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns the number of elements in the specified iterator that equal the 369090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * specified object. The iterator will be left exhausted: its 370090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code hasNext()} method will return {@code false}. 371090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 372090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @see Collections#frequency 373090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 374090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static int frequency(Iterator<?> iterator, @Nullable Object element) { 3750888a09821a98ac0680fad765217302858e70fa4Paul Duffin return size(filter(iterator, equalTo(element))); 376090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 377090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 378090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 379090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns an iterator that cycles indefinitely over the elements of {@code 380090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterable}. 381090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 382090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned iterator supports {@code remove()} if the provided iterator 383090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * does. After {@code remove()} is called, subsequent cycles omit the removed 384090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * element, which is no longer in {@code iterable}. The iterator's 385090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code hasNext()} method returns {@code true} until {@code iterable} is 386090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * empty. 387090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 388090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p><b>Warning:</b> Typical uses of the resulting iterator may produce an 389090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * infinite loop. You should use an explicit {@code break} or be certain that 390090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * you will eventually remove all the elements. 391090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 392090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> Iterator<T> cycle(final Iterable<T> iterable) { 393090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(iterable); 394090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new Iterator<T>() { 395090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<T> iterator = emptyIterator(); 396090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<T> removeFrom; 397090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 3980888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 399090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasNext() { 400090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!iterator.hasNext()) { 401090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson iterator = iterable.iterator(); 402090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 403090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.hasNext(); 404090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 4050888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 406090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public T next() { 407090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!hasNext()) { 408090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson throw new NoSuchElementException(); 409090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 410090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson removeFrom = iterator; 411090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.next(); 412090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 4130888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 414090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public void remove() { 4150888a09821a98ac0680fad765217302858e70fa4Paul Duffin checkRemove(removeFrom != null); 416090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson removeFrom.remove(); 417090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson removeFrom = null; 418090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 419090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 420090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 421090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 422090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 423090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns an iterator that cycles indefinitely over the provided elements. 424090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 4257dd252788645e940eada959bdde927426e2531c9Paul Duffin * <p>The returned iterator supports {@code remove()}. After {@code remove()} 4267dd252788645e940eada959bdde927426e2531c9Paul Duffin * is called, subsequent cycles omit the removed 427090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * element, but {@code elements} does not change. The iterator's 428090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code hasNext()} method returns {@code true} until all of the original 429090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * elements have been removed. 430090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 431090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p><b>Warning:</b> Typical uses of the resulting iterator may produce an 432090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * infinite loop. You should use an explicit {@code break} or be certain that 433090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * you will eventually remove all the elements. 434090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 435090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> Iterator<T> cycle(T... elements) { 436090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return cycle(Lists.newArrayList(elements)); 437090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 438090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 439090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 440090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Combines two iterators into a single iterator. The returned iterator 441090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterates across the elements in {@code a}, followed by the elements in 442090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code b}. The source iterators are not polled until necessary. 443090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 444090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned iterator supports {@code remove()} when the corresponding 445090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * input iterator supports it. 4467dd252788645e940eada959bdde927426e2531c9Paul Duffin * 4477dd252788645e940eada959bdde927426e2531c9Paul Duffin * <p><b>Note:</b> the current implementation is not suitable for nested 4487dd252788645e940eada959bdde927426e2531c9Paul Duffin * concatenated iterators, i.e. the following should be avoided when in a loop: 4497dd252788645e940eada959bdde927426e2531c9Paul Duffin * {@code iterator = Iterators.concat(iterator, suffix);}, since iteration over the 4507dd252788645e940eada959bdde927426e2531c9Paul Duffin * resulting iterator has a cubic complexity to the depth of the nesting. 451090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 4520888a09821a98ac0680fad765217302858e70fa4Paul Duffin public static <T> Iterator<T> concat(Iterator<? extends T> a, 4530888a09821a98ac0680fad765217302858e70fa4Paul Duffin Iterator<? extends T> b) { 4540888a09821a98ac0680fad765217302858e70fa4Paul Duffin return concat(ImmutableList.of(a, b).iterator()); 455090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 456090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 457090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 458090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Combines three iterators into a single iterator. The returned iterator 459090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterates across the elements in {@code a}, followed by the elements in 460090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code b}, followed by the elements in {@code c}. The source iterators 461090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * are not polled until necessary. 462090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 463090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned iterator supports {@code remove()} when the corresponding 464090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * input iterator supports it. 4657dd252788645e940eada959bdde927426e2531c9Paul Duffin * 4667dd252788645e940eada959bdde927426e2531c9Paul Duffin * <p><b>Note:</b> the current implementation is not suitable for nested 4677dd252788645e940eada959bdde927426e2531c9Paul Duffin * concatenated iterators, i.e. the following should be avoided when in a loop: 4687dd252788645e940eada959bdde927426e2531c9Paul Duffin * {@code iterator = Iterators.concat(iterator, suffix);}, since iteration over the 4697dd252788645e940eada959bdde927426e2531c9Paul Duffin * resulting iterator has a cubic complexity to the depth of the nesting. 470090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 4710888a09821a98ac0680fad765217302858e70fa4Paul Duffin public static <T> Iterator<T> concat(Iterator<? extends T> a, 4720888a09821a98ac0680fad765217302858e70fa4Paul Duffin Iterator<? extends T> b, Iterator<? extends T> c) { 4730888a09821a98ac0680fad765217302858e70fa4Paul Duffin return concat(ImmutableList.of(a, b, c).iterator()); 474090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 475090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 476090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 477090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Combines four iterators into a single iterator. The returned iterator 478090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterates across the elements in {@code a}, followed by the elements in 479090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code b}, followed by the elements in {@code c}, followed by the elements 480090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * in {@code d}. The source iterators are not polled until necessary. 481090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 482090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned iterator supports {@code remove()} when the corresponding 483090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * input iterator supports it. 4847dd252788645e940eada959bdde927426e2531c9Paul Duffin * 4857dd252788645e940eada959bdde927426e2531c9Paul Duffin * <p><b>Note:</b> the current implementation is not suitable for nested 4867dd252788645e940eada959bdde927426e2531c9Paul Duffin * concatenated iterators, i.e. the following should be avoided when in a loop: 4877dd252788645e940eada959bdde927426e2531c9Paul Duffin * {@code iterator = Iterators.concat(iterator, suffix);}, since iteration over the 4887dd252788645e940eada959bdde927426e2531c9Paul Duffin * resulting iterator has a cubic complexity to the depth of the nesting. 489090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 4900888a09821a98ac0680fad765217302858e70fa4Paul Duffin public static <T> Iterator<T> concat(Iterator<? extends T> a, 4910888a09821a98ac0680fad765217302858e70fa4Paul Duffin Iterator<? extends T> b, Iterator<? extends T> c, 4920888a09821a98ac0680fad765217302858e70fa4Paul Duffin Iterator<? extends T> d) { 4930888a09821a98ac0680fad765217302858e70fa4Paul Duffin return concat(ImmutableList.of(a, b, c, d).iterator()); 494090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 495090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 496090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 497090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Combines multiple iterators into a single iterator. The returned iterator 498090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterates across the elements of each iterator in {@code inputs}. The input 499090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterators are not polled until necessary. 500090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 501090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned iterator supports {@code remove()} when the corresponding 502090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * input iterator supports it. 503090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 5047dd252788645e940eada959bdde927426e2531c9Paul Duffin * <p><b>Note:</b> the current implementation is not suitable for nested 5057dd252788645e940eada959bdde927426e2531c9Paul Duffin * concatenated iterators, i.e. the following should be avoided when in a loop: 5067dd252788645e940eada959bdde927426e2531c9Paul Duffin * {@code iterator = Iterators.concat(iterator, suffix);}, since iteration over the 5077dd252788645e940eada959bdde927426e2531c9Paul Duffin * resulting iterator has a cubic complexity to the depth of the nesting. 5087dd252788645e940eada959bdde927426e2531c9Paul Duffin * 509090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws NullPointerException if any of the provided iterators is null 510090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 511090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> Iterator<T> concat(Iterator<? extends T>... inputs) { 5121d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return concat(ImmutableList.copyOf(inputs).iterator()); 513090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 514090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 515090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 516090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Combines multiple iterators into a single iterator. The returned iterator 517090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterates across the elements of each iterator in {@code inputs}. The input 518090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterators are not polled until necessary. 519090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 520090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned iterator supports {@code remove()} when the corresponding 521090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * input iterator supports it. The methods of the returned iterator may throw 5221d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code NullPointerException} if any of the input iterators is null. 5237dd252788645e940eada959bdde927426e2531c9Paul Duffin * 5247dd252788645e940eada959bdde927426e2531c9Paul Duffin * <p><b>Note:</b> the current implementation is not suitable for nested 5257dd252788645e940eada959bdde927426e2531c9Paul Duffin * concatenated iterators, i.e. the following should be avoided when in a loop: 5267dd252788645e940eada959bdde927426e2531c9Paul Duffin * {@code iterator = Iterators.concat(iterator, suffix);}, since iteration over the 5277dd252788645e940eada959bdde927426e2531c9Paul Duffin * resulting iterator has a cubic complexity to the depth of the nesting. 528090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 5290888a09821a98ac0680fad765217302858e70fa4Paul Duffin public static <T> Iterator<T> concat( 5300888a09821a98ac0680fad765217302858e70fa4Paul Duffin final Iterator<? extends Iterator<? extends T>> inputs) { 531090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(inputs); 532090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new Iterator<T>() { 533090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<? extends T> current = emptyIterator(); 534090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<? extends T> removeFrom; 535090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 5360888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 537090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasNext() { 538090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // http://code.google.com/p/google-collections/issues/detail?id=151 539090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // current.hasNext() might be relatively expensive, worth minimizing. 540090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson boolean currentHasNext; 5411d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert // checkNotNull eager for GWT 5421d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert // note: it must be here & not where 'current' is assigned, 5431d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert // because otherwise we'll have called inputs.next() before throwing 5441d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert // the first NPE, and the next time around we'll call inputs.next() 5451d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert // again, incorrectly moving beyond the error. 5460888a09821a98ac0680fad765217302858e70fa4Paul Duffin while (!(currentHasNext = checkNotNull(current).hasNext()) 5470888a09821a98ac0680fad765217302858e70fa4Paul Duffin && inputs.hasNext()) { 548090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson current = inputs.next(); 549090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 550090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return currentHasNext; 551090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 5520888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 553090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public T next() { 554090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!hasNext()) { 555090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson throw new NoSuchElementException(); 556090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 557090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson removeFrom = current; 558090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return current.next(); 559090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 5600888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 561090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public void remove() { 5620888a09821a98ac0680fad765217302858e70fa4Paul Duffin checkRemove(removeFrom != null); 563090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson removeFrom.remove(); 564090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson removeFrom = null; 565090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 566090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 567090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 568090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 569090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 570090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Divides an iterator into unmodifiable sublists of the given size (the final 571090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * list may be smaller). For example, partitioning an iterator containing 572090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code [a, b, c, d, e]} with a partition size of 3 yields {@code 573090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * [[a, b, c], [d, e]]} -- an outer iterator containing two inner lists of 574090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * three and two elements, all in the original order. 575090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 576090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned lists implement {@link java.util.RandomAccess}. 577090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 578090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param iterator the iterator to return a partitioned view of 579090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param size the desired size of each partition (the last may be smaller) 580090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @return an iterator of immutable lists containing the elements of {@code 581090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterator} divided into partitions 582090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws IllegalArgumentException if {@code size} is nonpositive 583090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 5840888a09821a98ac0680fad765217302858e70fa4Paul Duffin public static <T> UnmodifiableIterator<List<T>> partition( 5850888a09821a98ac0680fad765217302858e70fa4Paul Duffin Iterator<T> iterator, int size) { 586090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return partitionImpl(iterator, size, false); 587090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 588090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 589090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 590090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Divides an iterator into unmodifiable sublists of the given size, padding 591090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * the final iterator with null values if necessary. For example, partitioning 592090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * an iterator containing {@code [a, b, c, d, e]} with a partition size of 3 593090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * yields {@code [[a, b, c], [d, e, null]]} -- an outer iterator containing 594090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * two inner lists of three elements each, all in the original order. 595090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 596090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned lists implement {@link java.util.RandomAccess}. 597090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 598090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param iterator the iterator to return a partitioned view of 599090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param size the desired size of each partition 600090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @return an iterator of immutable lists containing the elements of {@code 601090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterator} divided into partitions (the final iterable may have 602090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * trailing null elements) 603090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws IllegalArgumentException if {@code size} is nonpositive 604090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 6050888a09821a98ac0680fad765217302858e70fa4Paul Duffin public static <T> UnmodifiableIterator<List<T>> paddedPartition( 6060888a09821a98ac0680fad765217302858e70fa4Paul Duffin Iterator<T> iterator, int size) { 607090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return partitionImpl(iterator, size, true); 608090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 609090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 6100888a09821a98ac0680fad765217302858e70fa4Paul Duffin private static <T> UnmodifiableIterator<List<T>> partitionImpl( 6110888a09821a98ac0680fad765217302858e70fa4Paul Duffin final Iterator<T> iterator, final int size, final boolean pad) { 612090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(iterator); 613090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkArgument(size > 0); 614090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new UnmodifiableIterator<List<T>>() { 6150888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 616090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasNext() { 617090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.hasNext(); 618090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 6190888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 620090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public List<T> next() { 621090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!hasNext()) { 622090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson throw new NoSuchElementException(); 623090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 624090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Object[] array = new Object[size]; 625090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson int count = 0; 626090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson for (; count < size && iterator.hasNext(); count++) { 627090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson array[count] = iterator.next(); 628090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 6291d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert for (int i = count; i < size; i++) { 6301d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert array[i] = null; // for GWT 6311d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 632090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 6330888a09821a98ac0680fad765217302858e70fa4Paul Duffin @SuppressWarnings("unchecked") // we only put Ts in it 6340888a09821a98ac0680fad765217302858e70fa4Paul Duffin List<T> list = Collections.unmodifiableList( 6350888a09821a98ac0680fad765217302858e70fa4Paul Duffin (List<T>) Arrays.asList(array)); 6361d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return (pad || count == size) ? list : list.subList(0, count); 637090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 638090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 639090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 640090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 641090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 642090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns the elements of {@code unfiltered} that satisfy a predicate. 643090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 6440888a09821a98ac0680fad765217302858e70fa4Paul Duffin public static <T> UnmodifiableIterator<T> filter( 6450888a09821a98ac0680fad765217302858e70fa4Paul Duffin final Iterator<T> unfiltered, final Predicate<? super T> predicate) { 646090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(unfiltered); 647090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(predicate); 648090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new AbstractIterator<T>() { 6490888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override protected T computeNext() { 650090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (unfiltered.hasNext()) { 651090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson T element = unfiltered.next(); 652090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (predicate.apply(element)) { 653090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return element; 654090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 655090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 656090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return endOfData(); 657090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 658090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 659090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 660090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 661090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 662090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns all instances of class {@code type} in {@code unfiltered}. The 663090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * returned iterator has elements whose class is {@code type} or a subclass of 664090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code type}. 665090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 666090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param unfiltered an iterator containing objects of any type 667090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param type the type of elements desired 668090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @return an unmodifiable iterator containing all elements of the original 669090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterator that were of the requested type 670090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 6710888a09821a98ac0680fad765217302858e70fa4Paul Duffin @SuppressWarnings("unchecked") // can cast to <T> because non-Ts are removed 672090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @GwtIncompatible("Class.isInstance") 6730888a09821a98ac0680fad765217302858e70fa4Paul Duffin public static <T> UnmodifiableIterator<T> filter( 6740888a09821a98ac0680fad765217302858e70fa4Paul Duffin Iterator<?> unfiltered, Class<T> type) { 6750888a09821a98ac0680fad765217302858e70fa4Paul Duffin return (UnmodifiableIterator<T>) filter(unfiltered, instanceOf(type)); 676090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 677090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 678090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 679090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns {@code true} if one or more elements returned by {@code iterator} 680090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * satisfy the given predicate. 681090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 6820888a09821a98ac0680fad765217302858e70fa4Paul Duffin public static <T> boolean any( 6830888a09821a98ac0680fad765217302858e70fa4Paul Duffin Iterator<T> iterator, Predicate<? super T> predicate) { 6840888a09821a98ac0680fad765217302858e70fa4Paul Duffin return indexOf(iterator, predicate) != -1; 685090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 686090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 687090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 688090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns {@code true} if every element returned by {@code iterator} 689090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * satisfies the given predicate. If {@code iterator} is empty, {@code true} 690090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * is returned. 691090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 6920888a09821a98ac0680fad765217302858e70fa4Paul Duffin public static <T> boolean all( 6930888a09821a98ac0680fad765217302858e70fa4Paul Duffin Iterator<T> iterator, Predicate<? super T> predicate) { 694090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(predicate); 695090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (iterator.hasNext()) { 696090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson T element = iterator.next(); 697090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!predicate.apply(element)) { 698090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return false; 699090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 700090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 701090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return true; 702090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 703090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 704090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 705090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns the first element in {@code iterator} that satisfies the given 7061d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * predicate; use this method only when such an element is known to exist. If 7071d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * no such element is found, the iterator will be left exhausted: its {@code 7081d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * hasNext()} method will return {@code false}. If it is possible that 7097dd252788645e940eada959bdde927426e2531c9Paul Duffin * <i>no</i> element will match, use {@link #tryFind} or {@link 7107dd252788645e940eada959bdde927426e2531c9Paul Duffin * #find(Iterator, Predicate, Object)} instead. 711090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 712090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws NoSuchElementException if no element in {@code iterator} matches 713090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * the given predicate 714090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 7150888a09821a98ac0680fad765217302858e70fa4Paul Duffin public static <T> T find( 7160888a09821a98ac0680fad765217302858e70fa4Paul Duffin Iterator<T> iterator, Predicate<? super T> predicate) { 717090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return filter(iterator, predicate).next(); 718090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 719090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 720090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 7211d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Returns the first element in {@code iterator} that satisfies the given 7221d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * predicate. If no such element is found, {@code defaultValue} will be 7231d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * returned from this method and the iterator will be left exhausted: its 7241d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code hasNext()} method will return {@code false}. Note that this can 7251d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * usually be handled more naturally using {@code 7261d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * tryFind(iterator, predicate).or(defaultValue)}. 7271d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 7281d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 7.0 7291d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 7307dd252788645e940eada959bdde927426e2531c9Paul Duffin @Nullable 7317dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> T find(Iterator<? extends T> iterator, Predicate<? super T> predicate, 7321d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Nullable T defaultValue) { 7330888a09821a98ac0680fad765217302858e70fa4Paul Duffin return getNext(filter(iterator, predicate), defaultValue); 7341d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 7351d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 7361d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 7371d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Returns an {@link Optional} containing the first element in {@code 7381d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * iterator} that satisfies the given predicate, if such an element exists. If 7391d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * no such element is found, an empty {@link Optional} will be returned from 7400888a09821a98ac0680fad765217302858e70fa4Paul Duffin * this method and the iterator will be left exhausted: its {@code 7411d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * hasNext()} method will return {@code false}. 7421d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 7431d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p><b>Warning:</b> avoid using a {@code predicate} that matches {@code 7441d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * null}. If {@code null} is matched in {@code iterator}, a 7451d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * NullPointerException will be thrown. 7461d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 7471d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 11.0 7481d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 7490888a09821a98ac0680fad765217302858e70fa4Paul Duffin public static <T> Optional<T> tryFind( 7500888a09821a98ac0680fad765217302858e70fa4Paul Duffin Iterator<T> iterator, Predicate<? super T> predicate) { 7511d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert UnmodifiableIterator<T> filteredIterator = filter(iterator, predicate); 7520888a09821a98ac0680fad765217302858e70fa4Paul Duffin return filteredIterator.hasNext() 7530888a09821a98ac0680fad765217302858e70fa4Paul Duffin ? Optional.of(filteredIterator.next()) 7540888a09821a98ac0680fad765217302858e70fa4Paul Duffin : Optional.<T>absent(); 7551d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 7561d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 7571d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 758bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * Returns the index in {@code iterator} of the first element that satisfies 759bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * the provided {@code predicate}, or {@code -1} if the Iterator has no such 760bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * elements. 761bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * 762bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * <p>More formally, returns the lowest index {@code i} such that 7631d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code predicate.apply(Iterators.get(iterator, i))} returns {@code true}, 7641d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * or {@code -1} if there is no such index. 765bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * 766bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * <p>If -1 is returned, the iterator will be left exhausted: its 767bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * {@code hasNext()} method will return {@code false}. Otherwise, 768bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * the iterator will be set to the element which satisfies the 769bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * {@code predicate}. 770bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * 7711d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 2.0 772bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor */ 7730888a09821a98ac0680fad765217302858e70fa4Paul Duffin public static <T> int indexOf( 7740888a09821a98ac0680fad765217302858e70fa4Paul Duffin Iterator<T> iterator, Predicate<? super T> predicate) { 7751d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkNotNull(predicate, "predicate"); 7760888a09821a98ac0680fad765217302858e70fa4Paul Duffin for (int i = 0; iterator.hasNext(); i++) { 777bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor T current = iterator.next(); 778bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor if (predicate.apply(current)) { 779bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor return i; 780bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor } 781bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor } 782bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor return -1; 783bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor } 784bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor 785bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor /** 786090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns an iterator that applies {@code function} to each element of {@code 787090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * fromIterator}. 788090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 789090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned iterator supports {@code remove()} if the provided iterator 790090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * does. After a successful {@code remove()} call, {@code fromIterator} no 791090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * longer contains the corresponding element. 792090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 793090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <F, T> Iterator<T> transform(final Iterator<F> fromIterator, 794090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson final Function<? super F, ? extends T> function) { 795090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(function); 7967dd252788645e940eada959bdde927426e2531c9Paul Duffin return new TransformedIterator<F, T>(fromIterator) { 7971d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 7987dd252788645e940eada959bdde927426e2531c9Paul Duffin T transform(F from) { 799090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return function.apply(from); 800090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 801090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 802090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 803090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 804090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 8051d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Advances {@code iterator} {@code position + 1} times, returning the 8061d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * element at the {@code position}th position. 807090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 808090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param position position of the element to return 809090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @return the element at the specified position in {@code iterator} 810090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws IndexOutOfBoundsException if {@code position} is negative or 811090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * greater than or equal to the number of elements remaining in 812090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code iterator} 813090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 814090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> T get(Iterator<T> iterator, int position) { 8151d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkNonnegative(position); 8160888a09821a98ac0680fad765217302858e70fa4Paul Duffin int skipped = advance(iterator, position); 8170888a09821a98ac0680fad765217302858e70fa4Paul Duffin if (!iterator.hasNext()) { 8180888a09821a98ac0680fad765217302858e70fa4Paul Duffin throw new IndexOutOfBoundsException("position (" + position 8190888a09821a98ac0680fad765217302858e70fa4Paul Duffin + ") must be less than the number of elements that remained (" 8200888a09821a98ac0680fad765217302858e70fa4Paul Duffin + skipped + ")"); 821090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 8220888a09821a98ac0680fad765217302858e70fa4Paul Duffin return iterator.next(); 823090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 824090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 8250888a09821a98ac0680fad765217302858e70fa4Paul Duffin static void checkNonnegative(int position) { 8261d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert if (position < 0) { 8270888a09821a98ac0680fad765217302858e70fa4Paul Duffin throw new IndexOutOfBoundsException("position (" + position 8280888a09821a98ac0680fad765217302858e70fa4Paul Duffin + ") must not be negative"); 8291d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 8301d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 8311d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 8321d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 8331d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Advances {@code iterator} {@code position + 1} times, returning the 8341d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * element at the {@code position}th position or {@code defaultValue} 8351d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * otherwise. 8361d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 8371d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @param position position of the element to return 8381d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @param defaultValue the default value to return if the iterator is empty 8391d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * or if {@code position} is greater than the number of elements 8401d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * remaining in {@code iterator} 8411d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @return the element at the specified position in {@code iterator} or 8421d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code defaultValue} if {@code iterator} produces fewer than 8431d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code position + 1} elements. 8441d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @throws IndexOutOfBoundsException if {@code position} is negative 8451d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 4.0 8461d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 8477dd252788645e940eada959bdde927426e2531c9Paul Duffin @Nullable 8487dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> T get(Iterator<? extends T> iterator, int position, @Nullable T defaultValue) { 8491d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkNonnegative(position); 8500888a09821a98ac0680fad765217302858e70fa4Paul Duffin advance(iterator, position); 8510888a09821a98ac0680fad765217302858e70fa4Paul Duffin return getNext(iterator, defaultValue); 8521d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 8531d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 8541d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 8551d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Returns the next element in {@code iterator} or {@code defaultValue} if 8561d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * the iterator is empty. The {@link Iterables} analog to this method is 8571d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@link Iterables#getFirst}. 8581d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 8591d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @param defaultValue the default value to return if the iterator is empty 8601d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @return the next element of {@code iterator} or the default value 8611d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 7.0 8621d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 8637dd252788645e940eada959bdde927426e2531c9Paul Duffin @Nullable 8647dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> T getNext(Iterator<? extends T> iterator, @Nullable T defaultValue) { 8651d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return iterator.hasNext() ? iterator.next() : defaultValue; 8661d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 8671d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 868090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 869090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Advances {@code iterator} to the end, returning the last element. 870090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 871090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @return the last element of {@code iterator} 8721d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @throws NoSuchElementException if the iterator is empty 873090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 874090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> T getLast(Iterator<T> iterator) { 875090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (true) { 876090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson T current = iterator.next(); 877090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!iterator.hasNext()) { 878090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return current; 879090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 880090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 881090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 882090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 883bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor /** 8841d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Advances {@code iterator} to the end, returning the last element or 8851d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code defaultValue} if the iterator is empty. 8861d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 8871d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @param defaultValue the default value to return if the iterator is empty 8881d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @return the last element of {@code iterator} 8891d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 3.0 8901d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 8917dd252788645e940eada959bdde927426e2531c9Paul Duffin @Nullable 8927dd252788645e940eada959bdde927426e2531c9Paul Duffin public static <T> T getLast(Iterator<? extends T> iterator, @Nullable T defaultValue) { 8931d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return iterator.hasNext() ? getLast(iterator) : defaultValue; 8941d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 8951d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 8961d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 8977dd252788645e940eada959bdde927426e2531c9Paul Duffin * Calls {@code next()} on {@code iterator}, either {@code numberToAdvance} times 8981d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * or until {@code hasNext()} returns {@code false}, whichever comes first. 8991d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 9007dd252788645e940eada959bdde927426e2531c9Paul Duffin * @return the number of elements the iterator was advanced 9017dd252788645e940eada959bdde927426e2531c9Paul Duffin * @since 13.0 (since 3.0 as {@code Iterators.skip}) 9021d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 9037dd252788645e940eada959bdde927426e2531c9Paul Duffin public static int advance(Iterator<?> iterator, int numberToAdvance) { 9041d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkNotNull(iterator); 9050888a09821a98ac0680fad765217302858e70fa4Paul Duffin checkArgument(numberToAdvance >= 0, "numberToAdvance must be nonnegative"); 9061d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 9071d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert int i; 9087dd252788645e940eada959bdde927426e2531c9Paul Duffin for (i = 0; i < numberToAdvance && iterator.hasNext(); i++) { 9091d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert iterator.next(); 9101d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 9111d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return i; 9121d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 9131d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 9141d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 9151d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Creates an iterator returning the first {@code limitSize} elements of the 9161d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * given iterator. If the original iterator does not contain that many 9171d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * elements, the returned iterator will have the same behavior as the original 9181d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * iterator. The returned iterator supports {@code remove()} if the original 9191d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * iterator does. 9201d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 9211d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @param iterator the iterator to limit 9221d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @param limitSize the maximum number of elements in the returned iterator 9231d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @throws IllegalArgumentException if {@code limitSize} is negative 9241d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 3.0 9251d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 9260888a09821a98ac0680fad765217302858e70fa4Paul Duffin public static <T> Iterator<T> limit( 9270888a09821a98ac0680fad765217302858e70fa4Paul Duffin final Iterator<T> iterator, final int limitSize) { 9281d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkNotNull(iterator); 9291d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkArgument(limitSize >= 0, "limit is negative"); 9301d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return new Iterator<T>() { 9311d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert private int count; 9321d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 9330888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 9341d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public boolean hasNext() { 9351d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return count < limitSize && iterator.hasNext(); 9361d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 9371d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 9380888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 9391d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public T next() { 9401d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert if (!hasNext()) { 9411d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert throw new NoSuchElementException(); 9421d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 9431d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert count++; 9441d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return iterator.next(); 9451d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 9461d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 9470888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 9481d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public void remove() { 9491d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert iterator.remove(); 9501d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 9511d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert }; 9521d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 9531d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 9541d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 955bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * Returns a view of the supplied {@code iterator} that removes each element 956bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * from the supplied {@code iterator} as it is returned. 957bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * 958bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * <p>The provided iterator must support {@link Iterator#remove()} or 959bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * else the returned iterator will fail on the first call to {@code 960bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * next}. 961bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * 962bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * @param iterator the iterator to remove and return elements from 963bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * @return an iterator that removes and returns elements from the 964bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * supplied iterator 9651d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 2.0 966bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor */ 967bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor public static <T> Iterator<T> consumingIterator(final Iterator<T> iterator) { 968bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor checkNotNull(iterator); 969bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor return new UnmodifiableIterator<T>() { 9700888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 971bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor public boolean hasNext() { 972bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor return iterator.hasNext(); 973bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor } 974bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor 9750888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 976bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor public T next() { 977bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor T next = iterator.next(); 978bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor iterator.remove(); 979bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor return next; 980bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor } 9810888a09821a98ac0680fad765217302858e70fa4Paul Duffin 9820888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 9830888a09821a98ac0680fad765217302858e70fa4Paul Duffin public String toString() { 9840888a09821a98ac0680fad765217302858e70fa4Paul Duffin return "Iterators.consumingIterator(...)"; 9850888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 986bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor }; 987bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor } 988bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor 9897dd252788645e940eada959bdde927426e2531c9Paul Duffin /** 9907dd252788645e940eada959bdde927426e2531c9Paul Duffin * Deletes and returns the next value from the iterator, or returns 9910888a09821a98ac0680fad765217302858e70fa4Paul Duffin * {@code null} if there is no such value. 9927dd252788645e940eada959bdde927426e2531c9Paul Duffin */ 9937dd252788645e940eada959bdde927426e2531c9Paul Duffin @Nullable 9947dd252788645e940eada959bdde927426e2531c9Paul Duffin static <T> T pollNext(Iterator<T> iterator) { 9957dd252788645e940eada959bdde927426e2531c9Paul Duffin if (iterator.hasNext()) { 9967dd252788645e940eada959bdde927426e2531c9Paul Duffin T result = iterator.next(); 9977dd252788645e940eada959bdde927426e2531c9Paul Duffin iterator.remove(); 9987dd252788645e940eada959bdde927426e2531c9Paul Duffin return result; 9997dd252788645e940eada959bdde927426e2531c9Paul Duffin } else { 10007dd252788645e940eada959bdde927426e2531c9Paul Duffin return null; 10017dd252788645e940eada959bdde927426e2531c9Paul Duffin } 10027dd252788645e940eada959bdde927426e2531c9Paul Duffin } 10037dd252788645e940eada959bdde927426e2531c9Paul Duffin 1004090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // Methods only in Iterators, not in Iterables 1005090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1006090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 10071d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Clears the iterator using its remove method. 10081d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 10091d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert static void clear(Iterator<?> iterator) { 10101d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkNotNull(iterator); 10111d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert while (iterator.hasNext()) { 10121d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert iterator.next(); 10131d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert iterator.remove(); 10141d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 10151d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 10161d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 10171d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 1018090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns an iterator containing the elements of {@code array} in order. The 1019090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * returned iterator is a view of the array; subsequent changes to the array 1020090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * will be reflected in the iterator. 1021090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1022090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p><b>Note:</b> It is often preferable to represent your data using a 1023090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * collection type, for example using {@link Arrays#asList(Object[])}, making 1024090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * this method unnecessary. 1025090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1026090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The {@code Iterable} equivalent of this method is either {@link 10271d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Arrays#asList(Object[])}, {@link ImmutableList#copyOf(Object[])}}, 10281d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * or {@link ImmutableList#of}. 1029090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 1030090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> UnmodifiableIterator<T> forArray(final T... array) { 10310888a09821a98ac0680fad765217302858e70fa4Paul Duffin return forArray(array, 0, array.length, 0); 1032090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1033090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1034090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 10357dd252788645e940eada959bdde927426e2531c9Paul Duffin * Returns a list iterator containing the elements in the specified range of 10367dd252788645e940eada959bdde927426e2531c9Paul Duffin * {@code array} in order, starting at the specified index. 1037090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1038090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The {@code Iterable} equivalent of this method is {@code 10397dd252788645e940eada959bdde927426e2531c9Paul Duffin * Arrays.asList(array).subList(offset, offset + length).listIterator(index)}. 1040090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 10410888a09821a98ac0680fad765217302858e70fa4Paul Duffin static <T> UnmodifiableListIterator<T> forArray( 10420888a09821a98ac0680fad765217302858e70fa4Paul Duffin final T[] array, final int offset, int length, int index) { 1043090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkArgument(length >= 0); 10441d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert int end = offset + length; 1045090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1046090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // Technically we should give a slightly more descriptive error on overflow 1047090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Preconditions.checkPositionIndexes(offset, end, array.length); 10480888a09821a98ac0680fad765217302858e70fa4Paul Duffin Preconditions.checkPositionIndex(index, length); 10490888a09821a98ac0680fad765217302858e70fa4Paul Duffin if (length == 0) { 10500888a09821a98ac0680fad765217302858e70fa4Paul Duffin return emptyListIterator(); 10510888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 1052090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 10531d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /* 10541d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * We can't use call the two-arg constructor with arguments (offset, end) 10551d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * because the returned Iterator is a ListIterator that may be moved back 10561d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * past the beginning of the iteration. 10571d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 10587dd252788645e940eada959bdde927426e2531c9Paul Duffin return new AbstractIndexedListIterator<T>(length, index) { 10590888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override protected T get(int index) { 10601d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return array[offset + index]; 1061090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1062090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 1063090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1064090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1065090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 1066090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns an iterator containing only {@code value}. 1067090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1068090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The {@link Iterable} equivalent of this method is {@link 1069090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Collections#singleton}. 1070090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 10710888a09821a98ac0680fad765217302858e70fa4Paul Duffin public static <T> UnmodifiableIterator<T> singletonIterator( 10720888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Nullable final T value) { 1073090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new UnmodifiableIterator<T>() { 1074090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson boolean done; 10750888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 1076090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasNext() { 1077090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return !done; 1078090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 10790888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 1080090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public T next() { 1081090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (done) { 1082090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson throw new NoSuchElementException(); 1083090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1084090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson done = true; 1085090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return value; 1086090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1087090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 1088090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1089090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1090090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 1091090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Adapts an {@code Enumeration} to the {@code Iterator} interface. 1092090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1093090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>This method has no equivalent in {@link Iterables} because viewing an 1094090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code Enumeration} as an {@code Iterable} is impossible. However, the 1095090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * contents can be <i>copied</i> into a collection using {@link 1096090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Collections#list}. 1097090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 10980888a09821a98ac0680fad765217302858e70fa4Paul Duffin public static <T> UnmodifiableIterator<T> forEnumeration( 10990888a09821a98ac0680fad765217302858e70fa4Paul Duffin final Enumeration<T> enumeration) { 1100090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(enumeration); 1101090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new UnmodifiableIterator<T>() { 11020888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 1103090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasNext() { 1104090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return enumeration.hasMoreElements(); 1105090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 11060888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 1107090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public T next() { 1108090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return enumeration.nextElement(); 1109090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1110090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 1111090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1112090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1113090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 1114090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Adapts an {@code Iterator} to the {@code Enumeration} interface. 1115090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1116090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The {@code Iterable} equivalent of this method is either {@link 1117090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Collections#enumeration} (if you have a {@link Collection}), or 1118090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code Iterators.asEnumeration(collection.iterator())}. 1119090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 1120090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> Enumeration<T> asEnumeration(final Iterator<T> iterator) { 1121090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(iterator); 1122090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new Enumeration<T>() { 11230888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 1124090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasMoreElements() { 1125090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.hasNext(); 1126090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 11270888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 1128090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public T nextElement() { 1129090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.next(); 1130090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1131090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 1132090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1133090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1134090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 1135090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Implementation of PeekingIterator that avoids peeking unless necessary. 1136090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 1137090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson private static class PeekingImpl<E> implements PeekingIterator<E> { 1138090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1139090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson private final Iterator<? extends E> iterator; 1140090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson private boolean hasPeeked; 1141090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson private E peekedElement; 1142090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1143090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public PeekingImpl(Iterator<? extends E> iterator) { 1144090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson this.iterator = checkNotNull(iterator); 1145090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1146090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 11470888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 1148090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasNext() { 1149090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return hasPeeked || iterator.hasNext(); 1150090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1151090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 11520888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 1153090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public E next() { 1154090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!hasPeeked) { 1155090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.next(); 1156090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1157090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson E result = peekedElement; 1158090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson hasPeeked = false; 1159090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson peekedElement = null; 1160090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return result; 1161090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1162090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 11630888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 1164090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public void remove() { 1165090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkState(!hasPeeked, "Can't remove after you've peeked at next"); 1166090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson iterator.remove(); 1167090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1168090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 11690888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 1170090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public E peek() { 1171090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!hasPeeked) { 1172090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson peekedElement = iterator.next(); 1173090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson hasPeeked = true; 1174090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1175090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return peekedElement; 1176090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1177090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1178090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1179090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 1180090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns a {@code PeekingIterator} backed by the given iterator. 1181090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1182090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>Calls to the {@code peek} method with no intervening calls to {@code 1183090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * next} do not affect the iteration, and hence return the same object each 1184090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * time. A subsequent call to {@code next} is guaranteed to return the same 1185090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * object again. For example: <pre> {@code 1186090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1187090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * PeekingIterator<String> peekingIterator = 1188090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Iterators.peekingIterator(Iterators.forArray("a", "b")); 1189090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * String a1 = peekingIterator.peek(); // returns "a" 1190090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * String a2 = peekingIterator.peek(); // also returns "a" 1191090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * String a3 = peekingIterator.next(); // also returns "a"}</pre> 1192090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 11930888a09821a98ac0680fad765217302858e70fa4Paul Duffin * <p>Any structural changes to the underlying iteration (aside from those 1194090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * performed by the iterator's own {@link PeekingIterator#remove()} method) 1195090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * will leave the iterator in an undefined state. 1196090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1197090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned iterator does not support removal after peeking, as 1198090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * explained by {@link PeekingIterator#remove()}. 1199090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1200090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>Note: If the given iterator is already a {@code PeekingIterator}, 1201090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * it <i>might</i> be returned to the caller, although this is neither 1202090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * guaranteed to occur nor required to be consistent. For example, this 1203090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * method <i>might</i> choose to pass through recognized implementations of 1204090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code PeekingIterator} when the behavior of the implementation is 1205090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * known to meet the contract guaranteed by this method. 1206090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1207090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>There is no {@link Iterable} equivalent to this method, so use this 1208090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * method to wrap each individual iterator as it is generated. 1209090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1210090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param iterator the backing iterator. The {@link PeekingIterator} assumes 1211090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * ownership of this iterator, so users should cease making direct calls 1212090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * to it after calling this method. 1213090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @return a peeking iterator backed by that iterator. Apart from the 1214090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * additional {@link PeekingIterator#peek()} method, this iterator behaves 1215090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * exactly the same as {@code iterator}. 1216090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 12170888a09821a98ac0680fad765217302858e70fa4Paul Duffin public static <T> PeekingIterator<T> peekingIterator( 12180888a09821a98ac0680fad765217302858e70fa4Paul Duffin Iterator<? extends T> iterator) { 1219090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (iterator instanceof PeekingImpl) { 1220090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // Safe to cast <? extends T> to <T> because PeekingImpl only uses T 1221090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // covariantly (and cannot be subclassed to add non-covariant uses). 1222090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @SuppressWarnings("unchecked") 1223090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson PeekingImpl<T> peeking = (PeekingImpl<T>) iterator; 1224090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return peeking; 1225090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1226090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new PeekingImpl<T>(iterator); 1227090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 12281d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 12291d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 12301d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Simply returns its argument. 12311d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 12321d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @deprecated no need to use this 12331d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 10.0 12341d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 12350888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Deprecated public static <T> PeekingIterator<T> peekingIterator( 12360888a09821a98ac0680fad765217302858e70fa4Paul Duffin PeekingIterator<T> iterator) { 12371d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return checkNotNull(iterator); 12381d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 12391d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 12401d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 12411d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Returns an iterator over the merged contents of all given 12421d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code iterators}, traversing every element of the input iterators. 12431d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Equivalent entries will not be de-duplicated. 12441d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 12451d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p>Callers must ensure that the source {@code iterators} are in 12461d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * non-descending order as this method does not sort its input. 12471d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 12481d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p>For any equivalent elements across all {@code iterators}, it is 12491d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * undefined which element is returned first. 12501d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 12511d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 11.0 12521d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 12531d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Beta 12541d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public static <T> UnmodifiableIterator<T> mergeSorted( 12550888a09821a98ac0680fad765217302858e70fa4Paul Duffin Iterable<? extends Iterator<? extends T>> iterators, 12560888a09821a98ac0680fad765217302858e70fa4Paul Duffin Comparator<? super T> comparator) { 12571d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkNotNull(iterators, "iterators"); 12581d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkNotNull(comparator, "comparator"); 12591d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 12601d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return new MergingIterator<T>(iterators, comparator); 12611d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 12621d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 12631d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 12641d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * An iterator that performs a lazy N-way merge, calculating the next value 12651d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * each time the iterator is polled. This amortizes the sorting cost over the 12661d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * iteration and requires less memory than sorting all elements at once. 12671d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 12681d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p>Retrieving a single element takes approximately O(log(M)) time, where M 12691d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * is the number of iterators. (Retrieving all elements takes approximately 12701d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * O(N*log(M)) time, where N is the total number of elements.) 12711d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 12720888a09821a98ac0680fad765217302858e70fa4Paul Duffin private static class MergingIterator<T> extends UnmodifiableIterator<T> { 12731d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert final Queue<PeekingIterator<T>> queue; 12741d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 12751d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public MergingIterator(Iterable<? extends Iterator<? extends T>> iterators, 12760888a09821a98ac0680fad765217302858e70fa4Paul Duffin final Comparator<? super T> itemComparator) { 12771d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert // A comparator that's used by the heap, allowing the heap 12781d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert // to be sorted based on the top of each iterator. 12790888a09821a98ac0680fad765217302858e70fa4Paul Duffin Comparator<PeekingIterator<T>> heapComparator = 12800888a09821a98ac0680fad765217302858e70fa4Paul Duffin new Comparator<PeekingIterator<T>>() { 12810888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 12820888a09821a98ac0680fad765217302858e70fa4Paul Duffin public int compare(PeekingIterator<T> o1, PeekingIterator<T> o2) { 12830888a09821a98ac0680fad765217302858e70fa4Paul Duffin return itemComparator.compare(o1.peek(), o2.peek()); 12840888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 12850888a09821a98ac0680fad765217302858e70fa4Paul Duffin }; 12861d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 12871d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert queue = new PriorityQueue<PeekingIterator<T>>(2, heapComparator); 12881d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 12891d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert for (Iterator<? extends T> iterator : iterators) { 12901d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert if (iterator.hasNext()) { 12911d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert queue.add(Iterators.peekingIterator(iterator)); 12921d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 12931d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 12941d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 12951d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 12961d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 12970888a09821a98ac0680fad765217302858e70fa4Paul Duffin public boolean hasNext() { 12980888a09821a98ac0680fad765217302858e70fa4Paul Duffin return !queue.isEmpty(); 12990888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 13001d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 13010888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 13020888a09821a98ac0680fad765217302858e70fa4Paul Duffin public T next() { 13030888a09821a98ac0680fad765217302858e70fa4Paul Duffin PeekingIterator<T> nextIter = queue.remove(); 13041d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert T next = nextIter.next(); 13051d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert if (nextIter.hasNext()) { 13061d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert queue.add(nextIter); 13071d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 13081d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return next; 13091d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 13101d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 13117dd252788645e940eada959bdde927426e2531c9Paul Duffin 13127dd252788645e940eada959bdde927426e2531c9Paul Duffin /** 13137dd252788645e940eada959bdde927426e2531c9Paul Duffin * Used to avoid http://bugs.sun.com/view_bug.do?bug_id=6558557 13147dd252788645e940eada959bdde927426e2531c9Paul Duffin */ 13157dd252788645e940eada959bdde927426e2531c9Paul Duffin static <T> ListIterator<T> cast(Iterator<T> iterator) { 13167dd252788645e940eada959bdde927426e2531c9Paul Duffin return (ListIterator<T>) iterator; 13177dd252788645e940eada959bdde927426e2531c9Paul Duffin } 1318090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson} 1319