Java tutorial
/* * Copyright (C) 2007 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 com.google.common.annotations.Beta; import com.google.common.annotations.GwtCompatible; import java.util.Collection; import java.util.Iterator; import java.util.List; import java.util.ListIterator; import javax.annotation.Nullable; /** * A list which forwards all its method calls to another list. Subclasses should * override one or more methods to modify the behavior of the backing list as * desired per the <a * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>. * * <p>This class does not implement {@link java.util.RandomAccess}. If the * delegate supports random access, the {@code ForwardingList} subclass should * implement the {@code RandomAccess} interface. * * <p><b>Warning:</b> The methods of {@code ForwardingList} forward * <b>indiscriminately</b> to the methods of the delegate. For example, * overriding {@link #add} alone <b>will not</b> change the behavior of {@link * #addAll}, which can lead to unexpected behavior. In this case, you should * override {@code addAll} as well, either providing your own implementation, or * delegating to the provided {@code standardAddAll} method. * * <p>The {@code standard} methods and any collection views they return are not * guaranteed to be thread-safe, even when all of the methods that they depend * on are thread-safe. * * @author Mike Bostock * @author Louis Wasserman * @since 2.0 */ @GwtCompatible public abstract class ForwardingList<E> extends ForwardingCollection<E> implements List<E> { // TODO(lowasser): identify places where thread safety is actually lost /** Constructor for use by subclasses. */ protected ForwardingList() { } @Override protected abstract List<E> delegate(); @Override public void add(int index, E element) { delegate().add(index, element); } @Override public boolean addAll(int index, Collection<? extends E> elements) { return delegate().addAll(index, elements); } @Override public E get(int index) { return delegate().get(index); } @Override public int indexOf(Object element) { return delegate().indexOf(element); } @Override public int lastIndexOf(Object element) { return delegate().lastIndexOf(element); } @Override public ListIterator<E> listIterator() { return delegate().listIterator(); } @Override public ListIterator<E> listIterator(int index) { return delegate().listIterator(index); } @Override public E remove(int index) { return delegate().remove(index); } @Override public E set(int index, E element) { return delegate().set(index, element); } @Override public List<E> subList(int fromIndex, int toIndex) { return delegate().subList(fromIndex, toIndex); } @Override public boolean equals(@Nullable Object object) { return object == this || delegate().equals(object); } @Override public int hashCode() { return delegate().hashCode(); } /** * A sensible default implementation of {@link #add(Object)}, in terms of * {@link #add(int, Object)}. If you override {@link #add(int, Object)}, you * may wish to override {@link #add(Object)} to forward to this * implementation. * * @since 7.0 */ protected boolean standardAdd(E element) { add(size(), element); return true; } /** * A sensible default implementation of {@link #addAll(int, Collection)}, in * terms of the {@code add} method of {@link #listIterator(int)}. If you * override {@link #listIterator(int)}, you may wish to override {@link * #addAll(int, Collection)} to forward to this implementation. * * @since 7.0 */ protected boolean standardAddAll(int index, Iterable<? extends E> elements) { return Lists.addAllImpl(this, index, elements); } /** * A sensible default implementation of {@link #indexOf}, in terms of {@link * #listIterator()}. If you override {@link #listIterator()}, you may wish to * override {@link #indexOf} to forward to this implementation. * * @since 7.0 */ protected int standardIndexOf(@Nullable Object element) { return Lists.indexOfImpl(this, element); } /** * A sensible default implementation of {@link #lastIndexOf}, in terms of * {@link #listIterator(int)}. If you override {@link #listIterator(int)}, you * may wish to override {@link #lastIndexOf} to forward to this * implementation. * * @since 7.0 */ protected int standardLastIndexOf(@Nullable Object element) { return Lists.lastIndexOfImpl(this, element); } /** * A sensible default implementation of {@link #iterator}, in terms of * {@link #listIterator()}. If you override {@link #listIterator()}, you may * wish to override {@link #iterator} to forward to this implementation. * * @since 7.0 */ protected Iterator<E> standardIterator() { return listIterator(); } /** * A sensible default implementation of {@link #listIterator()}, in terms of * {@link #listIterator(int)}. If you override {@link #listIterator(int)}, you * may wish to override {@link #listIterator()} to forward to this * implementation. * * @since 7.0 */ protected ListIterator<E> standardListIterator() { return listIterator(0); } /** * A sensible default implementation of {@link #listIterator(int)}, in terms * of {@link #size}, {@link #get(int)}, {@link #set(int, Object)}, {@link * #add(int, Object)}, and {@link #remove(int)}. If you override any of these * methods, you may wish to override {@link #listIterator(int)} to forward to * this implementation. * * @since 7.0 */ @Beta protected ListIterator<E> standardListIterator(int start) { return Lists.listIteratorImpl(this, start); } /** * A sensible default implementation of {@link #subList(int, int)}. If you * override any other methods, you may wish to override {@link #subList(int, * int)} to forward to this implementation. * * @since 7.0 */ @Beta protected List<E> standardSubList(int fromIndex, int toIndex) { return Lists.subListImpl(this, fromIndex, toIndex); } /** * A sensible definition of {@link #equals(Object)} in terms of {@link #size} * and {@link #iterator}. If you override either of those methods, you may * wish to override {@link #equals(Object)} to forward to this implementation. * * @since 7.0 */ @Beta protected boolean standardEquals(@Nullable Object object) { return Lists.equalsImpl(this, object); } /** * A sensible definition of {@link #hashCode} in terms of {@link #iterator}. * If you override {@link #iterator}, you may wish to override {@link * #hashCode} to forward to this implementation. * * @since 7.0 */ @Beta protected int standardHashCode() { return Lists.hashCodeImpl(this); } }