| /* |
| * 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.GwtCompatible; |
| import com.google.common.base.Objects; |
| import com.google.errorprone.annotations.CanIgnoreReturnValue; |
| import java.util.Collection; |
| import java.util.Iterator; |
| import org.checkerframework.checker.nullness.compatqual.NullableDecl; |
| |
| /** |
| * A collection which forwards all its method calls to another collection. Subclasses should |
| * override one or more methods to modify the behavior of the backing collection as desired per the |
| * <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>. |
| * |
| * <p><b>Warning:</b> The methods of {@code ForwardingCollection} 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><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code |
| * default} methods. Instead, it inherits their default implementations. When those implementations |
| * invoke methods, they invoke methods on the {@code ForwardingCollection}. |
| * |
| * <p>The {@code standard} methods are not guaranteed to be thread-safe, even when all of the |
| * methods that they depend on are thread-safe. |
| * |
| * @author Kevin Bourrillion |
| * @author Louis Wasserman |
| * @since 2.0 |
| */ |
| @GwtCompatible |
| public abstract class ForwardingCollection<E> extends ForwardingObject implements Collection<E> { |
| // TODO(lowasser): identify places where thread safety is actually lost |
| |
| /** Constructor for use by subclasses. */ |
| protected ForwardingCollection() {} |
| |
| @Override |
| protected abstract Collection<E> delegate(); |
| |
| @Override |
| public Iterator<E> iterator() { |
| return delegate().iterator(); |
| } |
| |
| @Override |
| public int size() { |
| return delegate().size(); |
| } |
| |
| @CanIgnoreReturnValue |
| @Override |
| public boolean removeAll(Collection<?> collection) { |
| return delegate().removeAll(collection); |
| } |
| |
| @Override |
| public boolean isEmpty() { |
| return delegate().isEmpty(); |
| } |
| |
| @Override |
| public boolean contains(Object object) { |
| return delegate().contains(object); |
| } |
| |
| @CanIgnoreReturnValue |
| @Override |
| public boolean add(E element) { |
| return delegate().add(element); |
| } |
| |
| @CanIgnoreReturnValue |
| @Override |
| public boolean remove(Object object) { |
| return delegate().remove(object); |
| } |
| |
| @Override |
| public boolean containsAll(Collection<?> collection) { |
| return delegate().containsAll(collection); |
| } |
| |
| @CanIgnoreReturnValue |
| @Override |
| public boolean addAll(Collection<? extends E> collection) { |
| return delegate().addAll(collection); |
| } |
| |
| @CanIgnoreReturnValue |
| @Override |
| public boolean retainAll(Collection<?> collection) { |
| return delegate().retainAll(collection); |
| } |
| |
| @Override |
| public void clear() { |
| delegate().clear(); |
| } |
| |
| @Override |
| public Object[] toArray() { |
| return delegate().toArray(); |
| } |
| |
| @CanIgnoreReturnValue |
| @Override |
| public <T> T[] toArray(T[] array) { |
| return delegate().toArray(array); |
| } |
| |
| /** |
| * A sensible definition of {@link #contains} in terms of {@link #iterator}. If you override |
| * {@link #iterator}, you may wish to override {@link #contains} to forward to this |
| * implementation. |
| * |
| * @since 7.0 |
| */ |
| protected boolean standardContains(@NullableDecl Object object) { |
| return Iterators.contains(iterator(), object); |
| } |
| |
| /** |
| * A sensible definition of {@link #containsAll} in terms of {@link #contains} . If you override |
| * {@link #contains}, you may wish to override {@link #containsAll} to forward to this |
| * implementation. |
| * |
| * @since 7.0 |
| */ |
| protected boolean standardContainsAll(Collection<?> collection) { |
| return Collections2.containsAllImpl(this, collection); |
| } |
| |
| /** |
| * A sensible definition of {@link #addAll} in terms of {@link #add}. If you override {@link |
| * #add}, you may wish to override {@link #addAll} to forward to this implementation. |
| * |
| * @since 7.0 |
| */ |
| protected boolean standardAddAll(Collection<? extends E> collection) { |
| return Iterators.addAll(this, collection.iterator()); |
| } |
| |
| /** |
| * A sensible definition of {@link #remove} in terms of {@link #iterator}, using the iterator's |
| * {@code remove} method. If you override {@link #iterator}, you may wish to override {@link |
| * #remove} to forward to this implementation. |
| * |
| * @since 7.0 |
| */ |
| protected boolean standardRemove(@NullableDecl Object object) { |
| Iterator<E> iterator = iterator(); |
| while (iterator.hasNext()) { |
| if (Objects.equal(iterator.next(), object)) { |
| iterator.remove(); |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| /** |
| * A sensible definition of {@link #removeAll} in terms of {@link #iterator}, using the iterator's |
| * {@code remove} method. If you override {@link #iterator}, you may wish to override {@link |
| * #removeAll} to forward to this implementation. |
| * |
| * @since 7.0 |
| */ |
| protected boolean standardRemoveAll(Collection<?> collection) { |
| return Iterators.removeAll(iterator(), collection); |
| } |
| |
| /** |
| * A sensible definition of {@link #retainAll} in terms of {@link #iterator}, using the iterator's |
| * {@code remove} method. If you override {@link #iterator}, you may wish to override {@link |
| * #retainAll} to forward to this implementation. |
| * |
| * @since 7.0 |
| */ |
| protected boolean standardRetainAll(Collection<?> collection) { |
| return Iterators.retainAll(iterator(), collection); |
| } |
| |
| /** |
| * A sensible definition of {@link #clear} in terms of {@link #iterator}, using the iterator's |
| * {@code remove} method. If you override {@link #iterator}, you may wish to override {@link |
| * #clear} to forward to this implementation. |
| * |
| * @since 7.0 |
| */ |
| protected void standardClear() { |
| Iterators.clear(iterator()); |
| } |
| |
| /** |
| * A sensible definition of {@link #isEmpty} as {@code !iterator().hasNext}. If you override |
| * {@link #isEmpty}, you may wish to override {@link #isEmpty} to forward to this implementation. |
| * Alternately, it may be more efficient to implement {@code isEmpty} as {@code size() == 0}. |
| * |
| * @since 7.0 |
| */ |
| protected boolean standardIsEmpty() { |
| return !iterator().hasNext(); |
| } |
| |
| /** |
| * A sensible definition of {@link #toString} in terms of {@link #iterator}. If you override |
| * {@link #iterator}, you may wish to override {@link #toString} to forward to this |
| * implementation. |
| * |
| * @since 7.0 |
| */ |
| protected String standardToString() { |
| return Collections2.toStringImpl(this); |
| } |
| |
| /** |
| * A sensible definition of {@link #toArray()} in terms of {@link #toArray(Object[])}. If you |
| * override {@link #toArray(Object[])}, you may wish to override {@link #toArray} to forward to |
| * this implementation. |
| * |
| * @since 7.0 |
| */ |
| protected Object[] standardToArray() { |
| Object[] newArray = new Object[size()]; |
| return toArray(newArray); |
| } |
| |
| /** |
| * A sensible definition of {@link #toArray(Object[])} in terms of {@link #size} and {@link |
| * #iterator}. If you override either of these methods, you may wish to override {@link #toArray} |
| * to forward to this implementation. |
| * |
| * @since 7.0 |
| */ |
| protected <T> T[] standardToArray(T[] array) { |
| return ObjectArrays.toArrayImpl(this, array); |
| } |
| } |