| /* |
| * Copyright (C) 2009 The Guava Authors |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package com.google.common.collect; |
| |
| import static com.google.common.base.Preconditions.checkNotNull; |
| |
| import com.google.common.annotations.GwtCompatible; |
| import com.google.common.base.Preconditions; |
| |
| import java.util.List; |
| import java.util.NoSuchElementException; |
| |
| import javax.annotation.Nullable; |
| |
| /** |
| * Implementation of {@link ImmutableList} with exactly one element. |
| * |
| * @author Hayward Chan |
| */ |
| @GwtCompatible(serializable = true, emulated = true) |
| @SuppressWarnings("serial") // uses writeReplace(), not default serialization |
| final class SingletonImmutableList<E> extends ImmutableList<E> { |
| |
| final transient E element; |
| |
| SingletonImmutableList(E element) { |
| this.element = checkNotNull(element); |
| } |
| |
| @Override |
| public E get(int index) { |
| Preconditions.checkElementIndex(index, 1); |
| return element; |
| } |
| |
| @Override public int indexOf(@Nullable Object object) { |
| return element.equals(object) ? 0 : -1; |
| } |
| |
| @Override public UnmodifiableIterator<E> iterator() { |
| return Iterators.singletonIterator(element); |
| } |
| |
| @Override public int lastIndexOf(@Nullable Object object) { |
| return element.equals(object) ? 0 : -1; |
| } |
| |
| @Override public UnmodifiableListIterator<E> listIterator(final int start) { |
| Preconditions.checkPositionIndex(start, 1); |
| return new UnmodifiableListIterator<E>() { |
| |
| boolean hasNext = start == 0; |
| |
| @Override public boolean hasNext() { |
| return hasNext; |
| } |
| |
| @Override public boolean hasPrevious() { |
| return !hasNext; |
| } |
| |
| @Override public E next() { |
| if (!hasNext) { |
| throw new NoSuchElementException(); |
| } |
| hasNext = false; |
| return element; |
| } |
| |
| @Override public int nextIndex() { |
| return hasNext ? 0 : 1; |
| } |
| |
| @Override public E previous() { |
| if (hasNext) { |
| throw new NoSuchElementException(); |
| } |
| hasNext = true; |
| return element; |
| } |
| |
| @Override public int previousIndex() { |
| return hasNext ? -1 : 0; |
| } |
| }; |
| } |
| |
| @Override |
| public int size() { |
| return 1; |
| } |
| |
| @Override public ImmutableList<E> subList(int fromIndex, int toIndex) { |
| Preconditions.checkPositionIndexes(fromIndex, toIndex, 1); |
| return (fromIndex == toIndex) ? ImmutableList.<E>of() : this; |
| } |
| |
| @Override public ImmutableList<E> reverse() { |
| return this; |
| } |
| |
| @Override public boolean contains(@Nullable Object object) { |
| return element.equals(object); |
| } |
| |
| @Override public boolean equals(Object object) { |
| if (object == this) { |
| return true; |
| } |
| if (object instanceof List) { |
| List<?> that = (List<?>) object; |
| return that.size() == 1 && element.equals(that.get(0)); |
| } |
| return false; |
| } |
| |
| @Override public int hashCode() { |
| // not caching hash code since it could change if the element is mutable |
| // in a way that modifies its hash code. |
| return 31 + element.hashCode(); |
| } |
| |
| @Override public String toString() { |
| String elementToString = element.toString(); |
| return new StringBuilder(elementToString.length() + 2) |
| .append('[') |
| .append(elementToString) |
| .append(']') |
| .toString(); |
| } |
| |
| @Override public boolean isEmpty() { |
| return false; |
| } |
| |
| @Override boolean isPartialView() { |
| return false; |
| } |
| |
| @Override public Object[] toArray() { |
| return new Object[] { element }; |
| } |
| |
| @Override public <T> T[] toArray(T[] array) { |
| if (array.length == 0) { |
| array = ObjectArrays.newArray(array, 1); |
| } else if (array.length > 1) { |
| array[1] = null; |
| } |
| // Writes will produce ArrayStoreException when the toArray() doc requires. |
| Object[] objectArray = array; |
| objectArray[0] = element; |
| return array; |
| } |
| } |