1090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson/* 21d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Copyright (C) 2009 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.checkNotNull; 201d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 21090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport com.google.common.annotations.GwtCompatible; 22090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport com.google.common.base.Preconditions; 23090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 24090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport java.util.List; 251d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport java.util.NoSuchElementException; 26090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 27090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport javax.annotation.Nullable; 28090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 29090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson/** 30090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Implementation of {@link ImmutableList} with exactly one element. 31090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 32090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @author Hayward Chan 33090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 341d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert@GwtCompatible(serializable = true, emulated = true) 35090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson@SuppressWarnings("serial") // uses writeReplace(), not default serialization 36090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonfinal class SingletonImmutableList<E> extends ImmutableList<E> { 371d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 38090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson final transient E element; 39090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 40090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson SingletonImmutableList(E element) { 41090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson this.element = checkNotNull(element); 42090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 43090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 441d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 45090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public E get(int index) { 46090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Preconditions.checkElementIndex(index, 1); 47090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return element; 48090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 49090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 50090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @Override public int indexOf(@Nullable Object object) { 51090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return element.equals(object) ? 0 : -1; 52090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 53090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 54090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @Override public UnmodifiableIterator<E> iterator() { 55090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return Iterators.singletonIterator(element); 56090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 57090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 58090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @Override public int lastIndexOf(@Nullable Object object) { 59090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return element.equals(object) ? 0 : -1; 60090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 61090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 621d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override public UnmodifiableListIterator<E> listIterator(final int start) { 631d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert Preconditions.checkPositionIndex(start, 1); 641d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return new UnmodifiableListIterator<E>() { 651d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 661d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert boolean hasNext = start == 0; 671d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 681d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override public boolean hasNext() { 691d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return hasNext; 701d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 711d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 721d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override public boolean hasPrevious() { 731d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return !hasNext; 741d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 751d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 761d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override public E next() { 771d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert if (!hasNext) { 781d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert throw new NoSuchElementException(); 791d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 801d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert hasNext = false; 811d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return element; 821d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 831d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 841d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override public int nextIndex() { 851d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return hasNext ? 0 : 1; 861d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 871d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 881d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override public E previous() { 891d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert if (hasNext) { 901d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert throw new NoSuchElementException(); 911d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 921d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert hasNext = true; 931d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return element; 941d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 951d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 961d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override public int previousIndex() { 971d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return hasNext ? -1 : 0; 981d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 991d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert }; 100090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 101090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1021d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override 103090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson public int size() { 104090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return 1; 105090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 106090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 107090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @Override public ImmutableList<E> subList(int fromIndex, int toIndex) { 108090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Preconditions.checkPositionIndexes(fromIndex, toIndex, 1); 109090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return (fromIndex == toIndex) ? ImmutableList.<E>of() : this; 110090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 111090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1121d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override public ImmutableList<E> reverse() { 1131d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return this; 1141d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 1151d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 116090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @Override public boolean contains(@Nullable Object object) { 117090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return element.equals(object); 118090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 119090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 120090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @Override public boolean equals(Object object) { 121090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (object == this) { 122090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return true; 123090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 124090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (object instanceof List) { 125090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson List<?> that = (List<?>) object; 126090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return that.size() == 1 && element.equals(that.get(0)); 127090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 128090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return false; 129090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 130090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 131090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @Override public int hashCode() { 132090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // not caching hash code since it could change if the element is mutable 133090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // in a way that modifies its hash code. 134090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return 31 + element.hashCode(); 135090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 136090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1371d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override public String toString() { 1381d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert String elementToString = element.toString(); 1391d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return new StringBuilder(elementToString.length() + 2) 1401d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert .append('[') 1411d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert .append(elementToString) 1421d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert .append(']') 1431d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert .toString(); 1441d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 1451d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 146090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @Override public boolean isEmpty() { 147090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return false; 148090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 149090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 1501d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override boolean isPartialView() { 1511d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return false; 1521d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 1531d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 154090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @Override public Object[] toArray() { 155090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return new Object[] { element }; 156090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 157090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 158090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson @Override public <T> T[] toArray(T[] array) { 159090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson if (array.length == 0) { 160090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson array = ObjectArrays.newArray(array, 1); 161090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } else if (array.length > 1) { 162090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson array[1] = null; 163090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 164090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson // Writes will produce ArrayStoreException when the toArray() doc requires. 165090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson Object[] objectArray = array; 166090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson objectArray[0] = element; 167090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson return array; 168090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson } 169090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson} 170