1090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson/* 21d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Copyright (C) 2007 The Guava Authors 3090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 4090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Licensed under the Apache License, Version 2.0 (the "License"); 5090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * you may not use this file except in compliance with the License. 6090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * You may obtain a copy of the License at 7090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 8090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * http://www.apache.org/licenses/LICENSE-2.0 9090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 10090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Unless required by applicable law or agreed to in writing, software 11090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * distributed under the License is distributed on an "AS IS" BASIS, 12090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * See the License for the specific language governing permissions and 14090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * limitations under the License. 15090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 16090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 17090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonpackage com.google.common.collect; 18090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 191d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport static com.google.common.base.Preconditions.checkArgument; 201d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport static com.google.common.base.Preconditions.checkNotNull; 211d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport static com.google.common.base.Preconditions.checkState; 221d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 231d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport com.google.common.annotations.Beta; 24090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport com.google.common.annotations.GwtCompatible; 25090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport com.google.common.base.Function; 26090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport com.google.common.base.Objects; 271d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport com.google.common.base.Optional; 28090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport com.google.common.base.Preconditions; 29090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport com.google.common.base.Predicate; 30090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 31090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport java.util.Arrays; 32090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport java.util.Collection; 33090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport java.util.Collections; 341d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport java.util.Comparator; 35090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport java.util.Enumeration; 36090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport java.util.Iterator; 37090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport java.util.List; 38090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport java.util.NoSuchElementException; 391d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport java.util.PriorityQueue; 401d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport java.util.Queue; 41090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 42090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport javax.annotation.Nullable; 43090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 44090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson/** 45090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * This class contains static utility methods that operate on or return objects 46090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * of type {@link Iterator}. Except as noted, each method has a corresponding 47090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@link Iterable}-based method in the {@link Iterables} class. 48090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 491d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p><i>Performance notes:</i> Unless otherwise noted, all of the iterators 501d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * produced in this class are <i>lazy</i>, which means that they only advance 511d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * the backing iteration when absolutely necessary. 521d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 53090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @author Kevin Bourrillion 54090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @author Jared Levy 551d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 2.0 (imported from Google Collections Library) 56090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 571d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert@GwtCompatible(emulated = true) 58090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonpublic final class Iterators { 59090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson private Iterators() {} 60090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 61090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson static final UnmodifiableIterator<Object> EMPTY_ITERATOR 62090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson = new UnmodifiableIterator<Object>() { 631d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 64090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasNext() { 65090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return false; 66090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 671d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 68090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public Object next() { 69090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson throw new NoSuchElementException(); 70090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 71090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 72090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 73090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 74090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns the empty iterator. 75090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 76090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The {@link Iterable} equivalent of this method is {@link 771d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * ImmutableSet#of()}. 78090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 79090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // Casting to any type is safe since there are no actual elements. 80090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @SuppressWarnings("unchecked") 81090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> UnmodifiableIterator<T> emptyIterator() { 82090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return (UnmodifiableIterator<T>) EMPTY_ITERATOR; 83090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 84090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 85090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson private static final Iterator<Object> EMPTY_MODIFIABLE_ITERATOR = 86090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson new Iterator<Object>() { 871d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override public boolean hasNext() { 88090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return false; 89090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 90090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 911d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override public Object next() { 92090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson throw new NoSuchElementException(); 93090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 94090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 951d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override public void remove() { 96090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson throw new IllegalStateException(); 97090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 98090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 99090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 100090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 101090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns the empty {@code Iterator} that throws 102090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@link IllegalStateException} instead of 103090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@link UnsupportedOperationException} on a call to 104090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@link Iterator#remove()}. 105090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 106090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // Casting to any type is safe since there are no actual elements. 107090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @SuppressWarnings("unchecked") 108090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson static <T> Iterator<T> emptyModifiableIterator() { 109090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return (Iterator<T>) EMPTY_MODIFIABLE_ITERATOR; 110090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 111090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 112090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** Returns an unmodifiable view of {@code iterator}. */ 113090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> UnmodifiableIterator<T> unmodifiableIterator( 114090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson final Iterator<T> iterator) { 115090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(iterator); 1161d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert if (iterator instanceof UnmodifiableIterator) { 1171d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return (UnmodifiableIterator<T>) iterator; 1181d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 119090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new UnmodifiableIterator<T>() { 1201d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 121090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasNext() { 122090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.hasNext(); 123090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1241d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 125090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public T next() { 126090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.next(); 127090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 128090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 129090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 130090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 131090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 1321d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Simply returns its argument. 1331d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 1341d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @deprecated no need to use this 1351d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 10.0 1361d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 1371d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Deprecated public static <T> UnmodifiableIterator<T> unmodifiableIterator( 1381d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert UnmodifiableIterator<T> iterator) { 1391d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return checkNotNull(iterator); 1401d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 1411d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 1421d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 143090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns the number of elements remaining in {@code iterator}. The iterator 144090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * will be left exhausted: its {@code hasNext()} method will return 145090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code false}. 146090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 147090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static int size(Iterator<?> iterator) { 148090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson int count = 0; 149090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (iterator.hasNext()) { 150090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson iterator.next(); 151090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson count++; 152090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 153090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return count; 154090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 155090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 156090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 157090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns {@code true} if {@code iterator} contains {@code element}. 158090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 159090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static boolean contains(Iterator<?> iterator, @Nullable Object element) 160090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson { 161090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (element == null) { 162090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (iterator.hasNext()) { 163090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (iterator.next() == null) { 164090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return true; 165090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 166090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 167090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } else { 168090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (iterator.hasNext()) { 169090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (element.equals(iterator.next())) { 170090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return true; 171090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 172090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 173090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 174090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return false; 175090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 176090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 177090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 178090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Traverses an iterator and removes every element that belongs to the 179090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * provided collection. The iterator will be left exhausted: its 180090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code hasNext()} method will return {@code false}. 181090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 182090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param removeFrom the iterator to (potentially) remove elements from 183090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param elementsToRemove the elements to remove 1841d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @return {@code true} if any element was removed from {@code iterator} 185090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 186090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static boolean removeAll( 187090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<?> removeFrom, Collection<?> elementsToRemove) { 188090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(elementsToRemove); 189090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson boolean modified = false; 190090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (removeFrom.hasNext()) { 191090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (elementsToRemove.contains(removeFrom.next())) { 192090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson removeFrom.remove(); 193090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson modified = true; 194090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 195090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 196090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return modified; 197090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 198090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 199090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 200090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Removes every element that satisfies the provided predicate from the 201090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterator. The iterator will be left exhausted: its {@code hasNext()} 202090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * method will return {@code false}. 203090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 204090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param removeFrom the iterator to (potentially) remove elements from 205090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param predicate a predicate that determines whether an element should 206090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * be removed 207090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @return {@code true} if any elements were removed from the iterator 2081d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 2.0 209090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 210bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor public static <T> boolean removeIf( 211090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<T> removeFrom, Predicate<? super T> predicate) { 212090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(predicate); 213090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson boolean modified = false; 214090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (removeFrom.hasNext()) { 215090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (predicate.apply(removeFrom.next())) { 216090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson removeFrom.remove(); 217090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson modified = true; 218090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 219090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 220090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return modified; 221090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 222090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 223090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 224090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Traverses an iterator and removes every element that does not belong to the 225090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * provided collection. The iterator will be left exhausted: its 226090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code hasNext()} method will return {@code false}. 227090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 228090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param removeFrom the iterator to (potentially) remove elements from 229090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param elementsToRetain the elements to retain 2301d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @return {@code true} if any element was removed from {@code iterator} 231090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 232090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static boolean retainAll( 233090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<?> removeFrom, Collection<?> elementsToRetain) { 234090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(elementsToRetain); 235090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson boolean modified = false; 236090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (removeFrom.hasNext()) { 237090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!elementsToRetain.contains(removeFrom.next())) { 238090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson removeFrom.remove(); 239090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson modified = true; 240090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 241090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 242090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return modified; 243090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 244090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 245090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 246090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Determines whether two iterators contain equal elements in the same order. 247090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * More specifically, this method returns {@code true} if {@code iterator1} 248090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * and {@code iterator2} contain the same number of elements and every element 249090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * of {@code iterator1} is equal to the corresponding element of 250090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code iterator2}. 251090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 252090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>Note that this will modify the supplied iterators, since they will have 253090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * been advanced some number of elements forward. 254090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 255090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static boolean elementsEqual( 256090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<?> iterator1, Iterator<?> iterator2) { 257090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (iterator1.hasNext()) { 258090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!iterator2.hasNext()) { 259090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return false; 260090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 261090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Object o1 = iterator1.next(); 262090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Object o2 = iterator2.next(); 263090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!Objects.equal(o1, o2)) { 264090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return false; 265090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 266090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 267090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return !iterator2.hasNext(); 268090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 269090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 270090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 271090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns a string representation of {@code iterator}, with the format 272090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code [e1, e2, ..., en]}. The iterator will be left exhausted: its 273090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code hasNext()} method will return {@code false}. 274090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 275090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static String toString(Iterator<?> iterator) { 276090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!iterator.hasNext()) { 277090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return "[]"; 278090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 279090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson StringBuilder builder = new StringBuilder(); 280090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson builder.append('[').append(iterator.next()); 281090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (iterator.hasNext()) { 282090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson builder.append(", ").append(iterator.next()); 283090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 284090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return builder.append(']').toString(); 285090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 286090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 287090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 288090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns the single element contained in {@code iterator}. 289090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 290090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws NoSuchElementException if the iterator is empty 291090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws IllegalArgumentException if the iterator contains multiple 292090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * elements. The state of the iterator is unspecified. 293090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 294090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> T getOnlyElement(Iterator<T> iterator) { 295090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson T first = iterator.next(); 296090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!iterator.hasNext()) { 297090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return first; 298090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 299090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 300090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson StringBuilder sb = new StringBuilder(); 301090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson sb.append("expected one element but was: <" + first); 302090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson for (int i = 0; i < 4 && iterator.hasNext(); i++) { 303090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson sb.append(", " + iterator.next()); 304090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 305090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (iterator.hasNext()) { 306090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson sb.append(", ..."); 307090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 3081d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert sb.append('>'); 309090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 310090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson throw new IllegalArgumentException(sb.toString()); 311090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 312090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 313090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 314090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns the single element contained in {@code iterator}, or {@code 315090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * defaultValue} if the iterator is empty. 316090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 317090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws IllegalArgumentException if the iterator contains multiple 318090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * elements. The state of the iterator is unspecified. 319090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 320090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> T getOnlyElement( 321090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<T> iterator, @Nullable T defaultValue) { 322090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.hasNext() ? getOnlyElement(iterator) : defaultValue; 323090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 324090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 325090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 326090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Adds all elements in {@code iterator} to {@code collection}. The iterator 327090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * will be left exhausted: its {@code hasNext()} method will return 328090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code false}. 329090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 330090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @return {@code true} if {@code collection} was modified as a result of this 331090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * operation 332090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 333090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> boolean addAll( 334090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Collection<T> addTo, Iterator<? extends T> iterator) { 335090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(addTo); 336090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson boolean wasModified = false; 337090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (iterator.hasNext()) { 338090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson wasModified |= addTo.add(iterator.next()); 339090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 340090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return wasModified; 341090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 342090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 343090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 344090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns the number of elements in the specified iterator that equal the 345090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * specified object. The iterator will be left exhausted: its 346090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code hasNext()} method will return {@code false}. 347090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 348090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @see Collections#frequency 349090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 350090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static int frequency(Iterator<?> iterator, @Nullable Object element) { 351090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson int result = 0; 352090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (element == null) { 353090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (iterator.hasNext()) { 354090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (iterator.next() == null) { 355090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson result++; 356090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 357090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 358090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } else { 359090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (iterator.hasNext()) { 360090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (element.equals(iterator.next())) { 361090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson result++; 362090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 363090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 364090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 365090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return result; 366090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 367090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 368090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 369090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns an iterator that cycles indefinitely over the elements of {@code 370090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterable}. 371090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 372090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned iterator supports {@code remove()} if the provided iterator 373090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * does. After {@code remove()} is called, subsequent cycles omit the removed 374090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * element, which is no longer in {@code iterable}. The iterator's 375090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code hasNext()} method returns {@code true} until {@code iterable} is 376090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * empty. 377090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 378090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p><b>Warning:</b> Typical uses of the resulting iterator may produce an 379090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * infinite loop. You should use an explicit {@code break} or be certain that 380090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * you will eventually remove all the elements. 381090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 382090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> Iterator<T> cycle(final Iterable<T> iterable) { 383090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(iterable); 384090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new Iterator<T>() { 385090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<T> iterator = emptyIterator(); 386090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<T> removeFrom; 387090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 3881d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 389090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasNext() { 390090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!iterator.hasNext()) { 391090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson iterator = iterable.iterator(); 392090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 393090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.hasNext(); 394090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 3951d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 396090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public T next() { 397090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!hasNext()) { 398090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson throw new NoSuchElementException(); 399090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 400090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson removeFrom = iterator; 401090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.next(); 402090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 4031d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 404090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public void remove() { 405090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkState(removeFrom != null, 406090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson "no calls to next() since last call to remove()"); 407090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson removeFrom.remove(); 408090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson removeFrom = null; 409090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 410090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 411090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 412090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 413090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 414090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns an iterator that cycles indefinitely over the provided elements. 415090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 416090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned iterator supports {@code remove()} if the provided iterator 417090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * does. After {@code remove()} is called, subsequent cycles omit the removed 418090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * element, but {@code elements} does not change. The iterator's 419090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code hasNext()} method returns {@code true} until all of the original 420090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * elements have been removed. 421090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 422090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p><b>Warning:</b> Typical uses of the resulting iterator may produce an 423090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * infinite loop. You should use an explicit {@code break} or be certain that 424090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * you will eventually remove all the elements. 425090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 426090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> Iterator<T> cycle(T... elements) { 427090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return cycle(Lists.newArrayList(elements)); 428090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 429090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 430090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 431090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Combines two iterators into a single iterator. The returned iterator 432090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterates across the elements in {@code a}, followed by the elements in 433090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code b}. The source iterators are not polled until necessary. 434090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 435090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned iterator supports {@code remove()} when the corresponding 436090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * input iterator supports it. 437090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 438090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @SuppressWarnings("unchecked") 439090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> Iterator<T> concat(Iterator<? extends T> a, 440090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<? extends T> b) { 441090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(a); 442090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(b); 443090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return concat(Arrays.asList(a, b).iterator()); 444090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 445090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 446090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 447090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Combines three iterators into a single iterator. The returned iterator 448090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterates across the elements in {@code a}, followed by the elements in 449090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code b}, followed by the elements in {@code c}. The source iterators 450090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * are not polled until necessary. 451090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 452090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned iterator supports {@code remove()} when the corresponding 453090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * input iterator supports it. 454090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 455090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @SuppressWarnings("unchecked") 456090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> Iterator<T> concat(Iterator<? extends T> a, 457090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<? extends T> b, Iterator<? extends T> c) { 458090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(a); 459090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(b); 460090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(c); 461090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return concat(Arrays.asList(a, b, c).iterator()); 462090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 463090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 464090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 465090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Combines four iterators into a single iterator. The returned iterator 466090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterates across the elements in {@code a}, followed by the elements in 467090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code b}, followed by the elements in {@code c}, followed by the elements 468090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * in {@code d}. The source iterators are not polled until necessary. 469090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 470090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned iterator supports {@code remove()} when the corresponding 471090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * input iterator supports it. 472090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 473090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @SuppressWarnings("unchecked") 474090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> Iterator<T> concat(Iterator<? extends T> a, 475090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<? extends T> b, Iterator<? extends T> c, 476090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<? extends T> d) { 477090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(a); 478090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(b); 479090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(c); 480090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(d); 481090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return concat(Arrays.asList(a, b, c, d).iterator()); 482090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 483090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 484090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 485090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Combines multiple iterators into a single iterator. The returned iterator 486090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterates across the elements of each iterator in {@code inputs}. The input 487090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterators are not polled until necessary. 488090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 489090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned iterator supports {@code remove()} when the corresponding 490090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * input iterator supports it. 491090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 492090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws NullPointerException if any of the provided iterators is null 493090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 494090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> Iterator<T> concat(Iterator<? extends T>... inputs) { 4951d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return concat(ImmutableList.copyOf(inputs).iterator()); 496090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 497090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 498090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 499090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Combines multiple iterators into a single iterator. The returned iterator 500090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterates across the elements of each iterator in {@code inputs}. The input 501090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterators are not polled until necessary. 502090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 503090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned iterator supports {@code remove()} when the corresponding 504090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * input iterator supports it. The methods of the returned iterator may throw 5051d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code NullPointerException} if any of the input iterators is null. 506090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 507090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> Iterator<T> concat( 508090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson final Iterator<? extends Iterator<? extends T>> inputs) { 509090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(inputs); 510090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new Iterator<T>() { 511090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<? extends T> current = emptyIterator(); 512090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<? extends T> removeFrom; 513090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 5141d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 515090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasNext() { 516090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // http://code.google.com/p/google-collections/issues/detail?id=151 517090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // current.hasNext() might be relatively expensive, worth minimizing. 518090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson boolean currentHasNext; 5191d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert // checkNotNull eager for GWT 5201d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert // note: it must be here & not where 'current' is assigned, 5211d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert // because otherwise we'll have called inputs.next() before throwing 5221d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert // the first NPE, and the next time around we'll call inputs.next() 5231d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert // again, incorrectly moving beyond the error. 5241d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert while (!(currentHasNext = checkNotNull(current).hasNext()) 5251d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert && inputs.hasNext()) { 526090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson current = inputs.next(); 527090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 528090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return currentHasNext; 529090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 5301d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 531090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public T next() { 532090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!hasNext()) { 533090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson throw new NoSuchElementException(); 534090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 535090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson removeFrom = current; 536090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return current.next(); 537090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 5381d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 539090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public void remove() { 540090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkState(removeFrom != null, 541090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson "no calls to next() since last call to remove()"); 542090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson removeFrom.remove(); 543090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson removeFrom = null; 544090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 545090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 546090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 547090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 548090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 549090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Divides an iterator into unmodifiable sublists of the given size (the final 550090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * list may be smaller). For example, partitioning an iterator containing 551090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code [a, b, c, d, e]} with a partition size of 3 yields {@code 552090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * [[a, b, c], [d, e]]} -- an outer iterator containing two inner lists of 553090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * three and two elements, all in the original order. 554090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 555090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned lists implement {@link java.util.RandomAccess}. 556090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 557090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param iterator the iterator to return a partitioned view of 558090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param size the desired size of each partition (the last may be smaller) 559090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @return an iterator of immutable lists containing the elements of {@code 560090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterator} divided into partitions 561090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws IllegalArgumentException if {@code size} is nonpositive 562090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 563090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> UnmodifiableIterator<List<T>> partition( 564090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<T> iterator, int size) { 565090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return partitionImpl(iterator, size, false); 566090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 567090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 568090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 569090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Divides an iterator into unmodifiable sublists of the given size, padding 570090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * the final iterator with null values if necessary. For example, partitioning 571090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * an iterator containing {@code [a, b, c, d, e]} with a partition size of 3 572090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * yields {@code [[a, b, c], [d, e, null]]} -- an outer iterator containing 573090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * two inner lists of three elements each, all in the original order. 574090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 575090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned lists implement {@link java.util.RandomAccess}. 576090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 577090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param iterator the iterator to return a partitioned view of 578090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param size the desired size of each partition 579090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @return an iterator of immutable lists containing the elements of {@code 580090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * iterator} divided into partitions (the final iterable may have 581090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * trailing null elements) 582090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws IllegalArgumentException if {@code size} is nonpositive 583090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 584090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> UnmodifiableIterator<List<T>> paddedPartition( 585090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<T> iterator, int size) { 586090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return partitionImpl(iterator, size, true); 587090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 588090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 589090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson private static <T> UnmodifiableIterator<List<T>> partitionImpl( 590090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson final Iterator<T> iterator, final int size, final boolean pad) { 591090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(iterator); 592090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkArgument(size > 0); 593090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new UnmodifiableIterator<List<T>>() { 5941d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 595090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasNext() { 596090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.hasNext(); 597090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 5981d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 599090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public List<T> next() { 600090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!hasNext()) { 601090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson throw new NoSuchElementException(); 602090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 603090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Object[] array = new Object[size]; 604090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson int count = 0; 605090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson for (; count < size && iterator.hasNext(); count++) { 606090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson array[count] = iterator.next(); 607090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 6081d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert for (int i = count; i < size; i++) { 6091d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert array[i] = null; // for GWT 6101d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 611090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 612090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @SuppressWarnings("unchecked") // we only put Ts in it 613090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson List<T> list = Collections.unmodifiableList( 614090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson (List<T>) Arrays.asList(array)); 6151d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return (pad || count == size) ? list : list.subList(0, count); 616090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 617090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 618090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 619090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 620090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 621090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns the elements of {@code unfiltered} that satisfy a predicate. 622090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 623090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> UnmodifiableIterator<T> filter( 624090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson final Iterator<T> unfiltered, final Predicate<? super T> predicate) { 625090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(unfiltered); 626090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(predicate); 627090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new AbstractIterator<T>() { 628090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @Override protected T computeNext() { 629090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (unfiltered.hasNext()) { 630090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson T element = unfiltered.next(); 631090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (predicate.apply(element)) { 632090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return element; 633090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 634090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 635090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return endOfData(); 636090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 637090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 638090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 639090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 640090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 641090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns {@code true} if one or more elements returned by {@code iterator} 642090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * satisfy the given predicate. 643090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 644090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> boolean any( 645090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<T> iterator, Predicate<? super T> predicate) { 646090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(predicate); 647090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (iterator.hasNext()) { 648090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson T element = iterator.next(); 649090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (predicate.apply(element)) { 650090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return true; 651090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 652090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 653090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return false; 654090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 655090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 656090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 657090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns {@code true} if every element returned by {@code iterator} 658090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * satisfies the given predicate. If {@code iterator} is empty, {@code true} 659090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * is returned. 660090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 661090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> boolean all( 662090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<T> iterator, Predicate<? super T> predicate) { 663090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(predicate); 664090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (iterator.hasNext()) { 665090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson T element = iterator.next(); 666090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!predicate.apply(element)) { 667090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return false; 668090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 669090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 670090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return true; 671090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 672090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 673090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 674090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns the first element in {@code iterator} that satisfies the given 6751d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * predicate; use this method only when such an element is known to exist. If 6761d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * no such element is found, the iterator will be left exhausted: its {@code 6771d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * hasNext()} method will return {@code false}. If it is possible that 6781d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <i>no</i> element will match, use {@link #tryFind)} or {@link 6791d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * #find(Iterator, Predicate, T)} instead. 680090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 681090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws NoSuchElementException if no element in {@code iterator} matches 682090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * the given predicate 683090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 6841d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public static <T> T find( 6851d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert Iterator<T> iterator, Predicate<? super T> predicate) { 686090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return filter(iterator, predicate).next(); 687090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 688090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 689090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 6901d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Returns the first element in {@code iterator} that satisfies the given 6911d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * predicate. If no such element is found, {@code defaultValue} will be 6921d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * returned from this method and the iterator will be left exhausted: its 6931d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code hasNext()} method will return {@code false}. Note that this can 6941d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * usually be handled more naturally using {@code 6951d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * tryFind(iterator, predicate).or(defaultValue)}. 6961d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 6971d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 7.0 6981d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 6991d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public static <T> T find(Iterator<T> iterator, Predicate<? super T> predicate, 7001d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Nullable T defaultValue) { 7011d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert UnmodifiableIterator<T> filteredIterator = filter(iterator, predicate); 7021d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return filteredIterator.hasNext() ? filteredIterator.next() : defaultValue; 7031d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 7041d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 7051d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 7061d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Returns an {@link Optional} containing the first element in {@code 7071d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * iterator} that satisfies the given predicate, if such an element exists. If 7081d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * no such element is found, an empty {@link Optional} will be returned from 7091d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * this method and the the iterator will be left exhausted: its {@code 7101d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * hasNext()} method will return {@code false}. 7111d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 7121d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p><b>Warning:</b> avoid using a {@code predicate} that matches {@code 7131d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * null}. If {@code null} is matched in {@code iterator}, a 7141d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * NullPointerException will be thrown. 7151d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 7161d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 11.0 7171d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 7181d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public static <T> Optional<T> tryFind( 7191d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert Iterator<T> iterator, Predicate<? super T> predicate) { 7201d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert UnmodifiableIterator<T> filteredIterator = filter(iterator, predicate); 7211d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return filteredIterator.hasNext() 7221d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert ? Optional.of(filteredIterator.next()) 7231d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert : Optional.<T>absent(); 7241d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 7251d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 7261d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 727bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * Returns the index in {@code iterator} of the first element that satisfies 728bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * the provided {@code predicate}, or {@code -1} if the Iterator has no such 729bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * elements. 730bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * 731bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * <p>More formally, returns the lowest index {@code i} such that 7321d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code predicate.apply(Iterators.get(iterator, i))} returns {@code true}, 7331d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * or {@code -1} if there is no such index. 734bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * 735bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * <p>If -1 is returned, the iterator will be left exhausted: its 736bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * {@code hasNext()} method will return {@code false}. Otherwise, 737bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * the iterator will be set to the element which satisfies the 738bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * {@code predicate}. 739bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * 7401d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 2.0 741bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor */ 742bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor public static <T> int indexOf( 743bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor Iterator<T> iterator, Predicate<? super T> predicate) { 7441d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkNotNull(predicate, "predicate"); 745bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor int i = 0; 746bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor while (iterator.hasNext()) { 747bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor T current = iterator.next(); 748bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor if (predicate.apply(current)) { 749bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor return i; 750bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor } 751bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor i++; 752bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor } 753bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor return -1; 754bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor } 755bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor 756bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor /** 757090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns an iterator that applies {@code function} to each element of {@code 758090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * fromIterator}. 759090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 760090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned iterator supports {@code remove()} if the provided iterator 761090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * does. After a successful {@code remove()} call, {@code fromIterator} no 762090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * longer contains the corresponding element. 763090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 764090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <F, T> Iterator<T> transform(final Iterator<F> fromIterator, 765090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson final Function<? super F, ? extends T> function) { 766090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(fromIterator); 767090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(function); 768090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new Iterator<T>() { 7691d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 770090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasNext() { 771090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return fromIterator.hasNext(); 772090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 7731d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 774090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public T next() { 775090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson F from = fromIterator.next(); 776090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return function.apply(from); 777090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 7781d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 779090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public void remove() { 780090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson fromIterator.remove(); 781090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 782090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 783090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 784090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 785090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 7861d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Advances {@code iterator} {@code position + 1} times, returning the 7871d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * element at the {@code position}th position. 788090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 789090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param position position of the element to return 790090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @return the element at the specified position in {@code iterator} 791090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws IndexOutOfBoundsException if {@code position} is negative or 792090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * greater than or equal to the number of elements remaining in 793090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code iterator} 794090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 795090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> T get(Iterator<T> iterator, int position) { 7961d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkNonnegative(position); 797090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 798090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson int skipped = 0; 799090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (iterator.hasNext()) { 800090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson T t = iterator.next(); 801090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (skipped++ == position) { 802090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return t; 803090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 804090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 805090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 806090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson throw new IndexOutOfBoundsException("position (" + position 807090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson + ") must be less than the number of elements that remained (" 808090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson + skipped + ")"); 809090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 810090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 8111d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert private static void checkNonnegative(int position) { 8121d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert if (position < 0) { 8131d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert throw new IndexOutOfBoundsException("position (" + position 8141d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert + ") must not be negative"); 8151d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 8161d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 8171d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 8181d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 8191d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Advances {@code iterator} {@code position + 1} times, returning the 8201d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * element at the {@code position}th position or {@code defaultValue} 8211d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * otherwise. 8221d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 8231d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @param position position of the element to return 8241d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @param defaultValue the default value to return if the iterator is empty 8251d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * or if {@code position} is greater than the number of elements 8261d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * remaining in {@code iterator} 8271d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @return the element at the specified position in {@code iterator} or 8281d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code defaultValue} if {@code iterator} produces fewer than 8291d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code position + 1} elements. 8301d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @throws IndexOutOfBoundsException if {@code position} is negative 8311d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 4.0 8321d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 8331d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public static <T> T get(Iterator<T> iterator, int position, 8341d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Nullable T defaultValue) { 8351d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkNonnegative(position); 8361d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 8371d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert try { 8381d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return get(iterator, position); 8391d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } catch (IndexOutOfBoundsException e) { 8401d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return defaultValue; 8411d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 8421d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 8431d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 8441d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 8451d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Returns the next element in {@code iterator} or {@code defaultValue} if 8461d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * the iterator is empty. The {@link Iterables} analog to this method is 8471d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@link Iterables#getFirst}. 8481d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 8491d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @param defaultValue the default value to return if the iterator is empty 8501d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @return the next element of {@code iterator} or the default value 8511d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 7.0 8521d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 8531d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public static <T> T getNext(Iterator<T> iterator, @Nullable T defaultValue) { 8541d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return iterator.hasNext() ? iterator.next() : defaultValue; 8551d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 8561d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 857090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 858090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Advances {@code iterator} to the end, returning the last element. 859090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 860090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @return the last element of {@code iterator} 8611d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @throws NoSuchElementException if the iterator is empty 862090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 863090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> T getLast(Iterator<T> iterator) { 864090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson while (true) { 865090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson T current = iterator.next(); 866090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!iterator.hasNext()) { 867090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return current; 868090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 869090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 870090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 871090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 872bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor /** 8731d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Advances {@code iterator} to the end, returning the last element or 8741d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code defaultValue} if the iterator is empty. 8751d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 8761d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @param defaultValue the default value to return if the iterator is empty 8771d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @return the last element of {@code iterator} 8781d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 3.0 8791d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 8801d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public static <T> T getLast(Iterator<T> iterator, @Nullable T defaultValue) { 8811d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return iterator.hasNext() ? getLast(iterator) : defaultValue; 8821d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 8831d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 8841d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 8851d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Calls {@code next()} on {@code iterator}, either {@code numberToSkip} times 8861d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * or until {@code hasNext()} returns {@code false}, whichever comes first. 8871d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 8881d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @return the number of elements skipped 8891d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 3.0 8901d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 8911d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Beta 8921d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public static <T> int skip(Iterator<T> iterator, int numberToSkip) { 8931d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkNotNull(iterator); 8941d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkArgument(numberToSkip >= 0, "number to skip cannot be negative"); 8951d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 8961d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert int i; 8971d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert for (i = 0; i < numberToSkip && iterator.hasNext(); i++) { 8981d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert iterator.next(); 8991d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 9001d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return i; 9011d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 9021d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 9031d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 9041d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Creates an iterator returning the first {@code limitSize} elements of the 9051d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * given iterator. If the original iterator does not contain that many 9061d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * elements, the returned iterator will have the same behavior as the original 9071d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * iterator. The returned iterator supports {@code remove()} if the original 9081d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * iterator does. 9091d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 9101d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @param iterator the iterator to limit 9111d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @param limitSize the maximum number of elements in the returned iterator 9121d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @throws IllegalArgumentException if {@code limitSize} is negative 9131d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 3.0 9141d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 9151d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public static <T> Iterator<T> limit( 9161d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert final Iterator<T> iterator, final int limitSize) { 9171d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkNotNull(iterator); 9181d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkArgument(limitSize >= 0, "limit is negative"); 9191d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return new Iterator<T>() { 9201d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert private int count; 9211d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 9221d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 9231d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public boolean hasNext() { 9241d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return count < limitSize && iterator.hasNext(); 9251d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 9261d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 9271d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 9281d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public T next() { 9291d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert if (!hasNext()) { 9301d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert throw new NoSuchElementException(); 9311d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 9321d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert count++; 9331d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return iterator.next(); 9341d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 9351d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 9361d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 9371d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public void remove() { 9381d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert iterator.remove(); 9391d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 9401d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert }; 9411d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 9421d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 9431d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 944bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * Returns a view of the supplied {@code iterator} that removes each element 945bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * from the supplied {@code iterator} as it is returned. 946bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * 947bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * <p>The provided iterator must support {@link Iterator#remove()} or 948bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * else the returned iterator will fail on the first call to {@code 949bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * next}. 950bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * 951bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * @param iterator the iterator to remove and return elements from 952bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * @return an iterator that removes and returns elements from the 953bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor * supplied iterator 9541d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 2.0 955bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor */ 956bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor public static <T> Iterator<T> consumingIterator(final Iterator<T> iterator) { 957bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor checkNotNull(iterator); 958bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor return new UnmodifiableIterator<T>() { 9591d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 960bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor public boolean hasNext() { 961bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor return iterator.hasNext(); 962bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor } 963bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor 9641d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 965bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor public T next() { 966bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor T next = iterator.next(); 967bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor iterator.remove(); 968bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor return next; 969bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor } 970bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor }; 971bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor } 972bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor 973090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // Methods only in Iterators, not in Iterables 974090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 975090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 9761d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Clears the iterator using its remove method. 9771d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 9781d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert static void clear(Iterator<?> iterator) { 9791d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkNotNull(iterator); 9801d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert while (iterator.hasNext()) { 9811d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert iterator.next(); 9821d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert iterator.remove(); 9831d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 9841d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 9851d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 9861d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 987090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns an iterator containing the elements of {@code array} in order. The 988090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * returned iterator is a view of the array; subsequent changes to the array 989090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * will be reflected in the iterator. 990090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 991090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p><b>Note:</b> It is often preferable to represent your data using a 992090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * collection type, for example using {@link Arrays#asList(Object[])}, making 993090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * this method unnecessary. 994090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 995090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The {@code Iterable} equivalent of this method is either {@link 9961d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Arrays#asList(Object[])}, {@link ImmutableList#copyOf(Object[])}}, 9971d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * or {@link ImmutableList#of}. 998090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 999090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> UnmodifiableIterator<T> forArray(final T... array) { 10001d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert // TODO(kevinb): compare performance with Arrays.asList(array).iterator(). 1001bfe2dd089341dcb4c1fb65a5b6b077ad0ebbf6dcDan Egnor checkNotNull(array); // eager for GWT. 10021d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return new AbstractIndexedListIterator<T>(array.length) { 10031d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override protected T get(int index) { 10041d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return array[index]; 1005090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1006090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 1007090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1008090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1009090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 1010090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns an iterator containing the elements in the specified range of 1011090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code array} in order. The returned iterator is a view of the array; 1012090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * subsequent changes to the array will be reflected in the iterator. 1013090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1014090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The {@code Iterable} equivalent of this method is {@code 1015090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Arrays.asList(array).subList(offset, offset + length)}. 1016090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1017090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param array array to read elements out of 1018090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param offset index of first array element to retrieve 1019090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param length number of elements in iteration 10201d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @throws IndexOutOfBoundsException if {@code offset} is negative, {@code 10211d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * length} is negative, or {@code offset + length > array.length} 1022090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 1023090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson static <T> UnmodifiableIterator<T> forArray( 1024090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson final T[] array, final int offset, int length) { 1025090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkArgument(length >= 0); 10261d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert int end = offset + length; 1027090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1028090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // Technically we should give a slightly more descriptive error on overflow 1029090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Preconditions.checkPositionIndexes(offset, end, array.length); 1030090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 10311d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /* 10321d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * We can't use call the two-arg constructor with arguments (offset, end) 10331d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * because the returned Iterator is a ListIterator that may be moved back 10341d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * past the beginning of the iteration. 10351d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 10361d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return new AbstractIndexedListIterator<T>(length) { 10371d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override protected T get(int index) { 10381d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return array[offset + index]; 1039090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1040090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 1041090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1042090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1043090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 1044090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns an iterator containing only {@code value}. 1045090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1046090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The {@link Iterable} equivalent of this method is {@link 1047090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Collections#singleton}. 1048090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 1049090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> UnmodifiableIterator<T> singletonIterator( 1050090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @Nullable final T value) { 1051090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new UnmodifiableIterator<T>() { 1052090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson boolean done; 10531d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 1054090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasNext() { 1055090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return !done; 1056090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 10571d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 1058090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public T next() { 1059090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (done) { 1060090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson throw new NoSuchElementException(); 1061090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1062090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson done = true; 1063090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return value; 1064090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1065090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 1066090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1067090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1068090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 1069090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Adapts an {@code Enumeration} to the {@code Iterator} interface. 1070090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1071090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>This method has no equivalent in {@link Iterables} because viewing an 1072090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code Enumeration} as an {@code Iterable} is impossible. However, the 1073090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * contents can be <i>copied</i> into a collection using {@link 1074090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Collections#list}. 1075090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 1076090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> UnmodifiableIterator<T> forEnumeration( 1077090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson final Enumeration<T> enumeration) { 1078090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(enumeration); 1079090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new UnmodifiableIterator<T>() { 10801d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 1081090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasNext() { 1082090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return enumeration.hasMoreElements(); 1083090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 10841d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 1085090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public T next() { 1086090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return enumeration.nextElement(); 1087090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1088090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 1089090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1090090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1091090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 1092090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Adapts an {@code Iterator} to the {@code Enumeration} interface. 1093090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1094090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The {@code Iterable} equivalent of this method is either {@link 1095090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Collections#enumeration} (if you have a {@link Collection}), or 1096090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code Iterators.asEnumeration(collection.iterator())}. 1097090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 1098090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> Enumeration<T> asEnumeration(final Iterator<T> iterator) { 1099090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkNotNull(iterator); 1100090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new Enumeration<T>() { 11011d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 1102090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasMoreElements() { 1103090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.hasNext(); 1104090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 11051d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 1106090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public T nextElement() { 1107090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.next(); 1108090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1109090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson }; 1110090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1111090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1112090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 1113090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Implementation of PeekingIterator that avoids peeking unless necessary. 1114090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 1115090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson private static class PeekingImpl<E> implements PeekingIterator<E> { 1116090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1117090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson private final Iterator<? extends E> iterator; 1118090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson private boolean hasPeeked; 1119090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson private E peekedElement; 1120090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1121090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public PeekingImpl(Iterator<? extends E> iterator) { 1122090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson this.iterator = checkNotNull(iterator); 1123090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1124090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 11251d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 1126090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public boolean hasNext() { 1127090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return hasPeeked || iterator.hasNext(); 1128090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1129090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 11301d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 1131090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public E next() { 1132090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!hasPeeked) { 1133090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return iterator.next(); 1134090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1135090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson E result = peekedElement; 1136090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson hasPeeked = false; 1137090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson peekedElement = null; 1138090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return result; 1139090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1140090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 11411d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 1142090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public void remove() { 1143090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson checkState(!hasPeeked, "Can't remove after you've peeked at next"); 1144090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson iterator.remove(); 1145090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1146090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 11471d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 1148090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public E peek() { 1149090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (!hasPeeked) { 1150090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson peekedElement = iterator.next(); 1151090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson hasPeeked = true; 1152090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1153090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return peekedElement; 1154090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1155090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1156090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1157090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 1158090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns a {@code PeekingIterator} backed by the given iterator. 1159090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1160090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>Calls to the {@code peek} method with no intervening calls to {@code 1161090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * next} do not affect the iteration, and hence return the same object each 1162090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * time. A subsequent call to {@code next} is guaranteed to return the same 1163090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * object again. For example: <pre> {@code 1164090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1165090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * PeekingIterator<String> peekingIterator = 1166090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Iterators.peekingIterator(Iterators.forArray("a", "b")); 1167090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * String a1 = peekingIterator.peek(); // returns "a" 1168090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * String a2 = peekingIterator.peek(); // also returns "a" 1169090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * String a3 = peekingIterator.next(); // also returns "a"}</pre> 1170090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1171090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Any structural changes to the underlying iteration (aside from those 1172090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * performed by the iterator's own {@link PeekingIterator#remove()} method) 1173090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * will leave the iterator in an undefined state. 1174090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1175090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The returned iterator does not support removal after peeking, as 1176090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * explained by {@link PeekingIterator#remove()}. 1177090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1178090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>Note: If the given iterator is already a {@code PeekingIterator}, 1179090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * it <i>might</i> be returned to the caller, although this is neither 1180090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * guaranteed to occur nor required to be consistent. For example, this 1181090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * method <i>might</i> choose to pass through recognized implementations of 1182090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@code PeekingIterator} when the behavior of the implementation is 1183090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * known to meet the contract guaranteed by this method. 1184090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1185090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>There is no {@link Iterable} equivalent to this method, so use this 1186090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * method to wrap each individual iterator as it is generated. 1187090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 1188090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @param iterator the backing iterator. The {@link PeekingIterator} assumes 1189090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * ownership of this iterator, so users should cease making direct calls 1190090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * to it after calling this method. 1191090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @return a peeking iterator backed by that iterator. Apart from the 1192090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * additional {@link PeekingIterator#peek()} method, this iterator behaves 1193090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * exactly the same as {@code iterator}. 1194090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 1195090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public static <T> PeekingIterator<T> peekingIterator( 1196090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Iterator<? extends T> iterator) { 1197090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (iterator instanceof PeekingImpl) { 1198090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // Safe to cast <? extends T> to <T> because PeekingImpl only uses T 1199090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // covariantly (and cannot be subclassed to add non-covariant uses). 1200090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @SuppressWarnings("unchecked") 1201090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson PeekingImpl<T> peeking = (PeekingImpl<T>) iterator; 1202090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return peeking; 1203090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 1204090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new PeekingImpl<T>(iterator); 1205090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 12061d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 12071d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 12081d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Simply returns its argument. 12091d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 12101d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @deprecated no need to use this 12111d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 10.0 12121d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 12131d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Deprecated public static <T> PeekingIterator<T> peekingIterator( 12141d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert PeekingIterator<T> iterator) { 12151d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return checkNotNull(iterator); 12161d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 12171d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 12181d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 12191d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Returns an iterator over the merged contents of all given 12201d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code iterators}, traversing every element of the input iterators. 12211d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Equivalent entries will not be de-duplicated. 12221d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 12231d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p>Callers must ensure that the source {@code iterators} are in 12241d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * non-descending order as this method does not sort its input. 12251d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 12261d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p>For any equivalent elements across all {@code iterators}, it is 12271d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * undefined which element is returned first. 12281d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 12291d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 11.0 12301d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 12311d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Beta 12321d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public static <T> UnmodifiableIterator<T> mergeSorted( 12331d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert Iterable<? extends Iterator<? extends T>> iterators, 12341d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert Comparator<? super T> comparator) { 12351d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkNotNull(iterators, "iterators"); 12361d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert checkNotNull(comparator, "comparator"); 12371d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 12381d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return new MergingIterator<T>(iterators, comparator); 12391d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 12401d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 12411d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 12421d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * An iterator that performs a lazy N-way merge, calculating the next value 12431d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * each time the iterator is polled. This amortizes the sorting cost over the 12441d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * iteration and requires less memory than sorting all elements at once. 12451d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 12461d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p>Retrieving a single element takes approximately O(log(M)) time, where M 12471d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * is the number of iterators. (Retrieving all elements takes approximately 12481d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * O(N*log(M)) time, where N is the total number of elements.) 12491d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 12501d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert private static class MergingIterator<T> extends AbstractIterator<T> { 12511d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert final Queue<PeekingIterator<T>> queue; 12521d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert final Comparator<? super T> comparator; 12531d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 12541d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public MergingIterator(Iterable<? extends Iterator<? extends T>> iterators, 12551d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert Comparator<? super T> itemComparator) { 12561d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert this.comparator = itemComparator; 12571d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 12581d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert // A comparator that's used by the heap, allowing the heap 12591d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert // to be sorted based on the top of each iterator. 12601d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert Comparator<PeekingIterator<T>> heapComparator = 12611d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert new Comparator<PeekingIterator<T>>() { 12621d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 12631d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public int compare(PeekingIterator<T> o1, PeekingIterator<T> o2) { 12641d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return comparator.compare(o1.peek(), o2.peek()); 12651d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 12661d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert }; 12671d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 12681d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert queue = new PriorityQueue<PeekingIterator<T>>(2, heapComparator); 12691d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 12701d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert for (Iterator<? extends T> iterator : iterators) { 12711d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert if (iterator.hasNext()) { 12721d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert queue.add(Iterators.peekingIterator(iterator)); 12731d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 12741d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 12751d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 12761d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 12771d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 12781d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert protected T computeNext() { 12791d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert if (queue.isEmpty()) { 12801d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return endOfData(); 12811d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 12821d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 12831d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert PeekingIterator<T> nextIter = queue.poll(); 12841d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert T next = nextIter.next(); 12851d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 12861d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert if (nextIter.hasNext()) { 12871d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert queue.add(nextIter); 12881d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 12891d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 12901d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return next; 12911d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 12921d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 1293090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson} 1294