1 /* 2 * Copyright (C) 2007 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.common.collect; 18 19 import com.google.common.annotations.Beta; 20 import com.google.common.annotations.GwtCompatible; 21 22 import java.util.Set; 23 24 import javax.annotation.Nullable; 25 26 /** 27 * A set which forwards all its method calls to another set. Subclasses should 28 * override one or more methods to modify the behavior of the backing set as 29 * desired per the <a 30 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>. 31 * 32 * <p><b>Warning:</b> The methods of {@code ForwardingSet} forward 33 * <b>indiscriminately</b> to the methods of the delegate. For example, 34 * overriding {@link #add} alone <b>will not</b> change the behavior of {@link 35 * #addAll}, which can lead to unexpected behavior. In this case, you should 36 * override {@code addAll} as well, either providing your own implementation, or 37 * delegating to the provided {@code standardAddAll} method. 38 * 39 * <p>The {@code standard} methods are not guaranteed to be thread-safe, even 40 * when all of the methods that they depend on are thread-safe. 41 * 42 * @author Kevin Bourrillion 43 * @author Louis Wasserman 44 * @since 2.0 (imported from Google Collections Library) 45 */ 46 @GwtCompatible 47 public abstract class ForwardingSet<E> extends ForwardingCollection<E> 48 implements Set<E> { 49 // TODO(user): identify places where thread safety is actually lost 50 51 /** Constructor for use by subclasses. */ 52 protected ForwardingSet() {} 53 54 @Override protected abstract Set<E> delegate(); 55 56 @Override public boolean equals(@Nullable Object object) { 57 return object == this || delegate().equals(object); 58 } 59 60 @Override public int hashCode() { 61 return delegate().hashCode(); 62 } 63 64 /** 65 * A sensible definition of {@link #equals} in terms of {@link #size} and 66 * {@link #containsAll}. If you override either of those methods, you may wish 67 * to override {@link #equals} to forward to this implementation. 68 * 69 * @since 7.0 70 */ 71 @Beta protected boolean standardEquals(@Nullable Object object) { 72 return Sets.equalsImpl(this, object); 73 } 74 75 /** 76 * A sensible definition of {@link #hashCode} in terms of {@link #iterator}. 77 * If you override {@link #iterator}, you may wish to override {@link #equals} 78 * to forward to this implementation. 79 * 80 * @since 7.0 81 */ 82 @Beta protected int standardHashCode() { 83 return Sets.hashCodeImpl(this); 84 } 85 } 86
