001/* 002 * Copyright (C) 2007 The Guava Authors 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * http://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package com.google.common.collect; 018 019import static com.google.common.collect.ForwardingSortedMap.unsafeCompare; 020 021import com.google.common.annotations.GwtCompatible; 022import java.util.Comparator; 023import java.util.Iterator; 024import java.util.NoSuchElementException; 025import java.util.SortedSet; 026import javax.annotation.CheckForNull; 027import org.checkerframework.checker.nullness.qual.Nullable; 028 029/** 030 * A sorted set which forwards all its method calls to another sorted set. Subclasses should 031 * override one or more methods to modify the behavior of the backing sorted set as desired per the 032 * <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>. 033 * 034 * <p><b>Warning:</b> The methods of {@code ForwardingSortedSet} forward <i>indiscriminately</i> to 035 * the methods of the delegate. For example, overriding {@link #add} alone <i>will not</i> change 036 * the behavior of {@link #addAll}, which can lead to unexpected behavior. In this case, you should 037 * override {@code addAll} as well, either providing your own implementation, or delegating to the 038 * provided {@code standardAddAll} method. 039 * 040 * <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code 041 * default} methods. Instead, it inherits their default implementations. When those implementations 042 * invoke methods, they invoke methods on the {@code ForwardingSortedSet}. 043 * 044 * <p>Each of the {@code standard} methods, where appropriate, uses the set's comparator (or the 045 * natural ordering of the elements, if there is no comparator) to test element equality. As a 046 * result, if the comparator is not consistent with equals, some of the standard implementations may 047 * violate the {@code Set} contract. 048 * 049 * <p>The {@code standard} methods and the collection views they return are not guaranteed to be 050 * thread-safe, even when all of the methods that they depend on are thread-safe. 051 * 052 * @author Mike Bostock 053 * @author Louis Wasserman 054 * @since 2.0 055 */ 056@GwtCompatible 057public abstract class ForwardingSortedSet<E extends @Nullable Object> extends ForwardingSet<E> 058 implements SortedSet<E> { 059 060 /** Constructor for use by subclasses. */ 061 protected ForwardingSortedSet() {} 062 063 @Override 064 protected abstract SortedSet<E> delegate(); 065 066 @Override 067 @CheckForNull 068 public Comparator<? super E> comparator() { 069 return delegate().comparator(); 070 } 071 072 @Override 073 @ParametricNullness 074 public E first() { 075 return delegate().first(); 076 } 077 078 @Override 079 public SortedSet<E> headSet(@ParametricNullness E toElement) { 080 return delegate().headSet(toElement); 081 } 082 083 @Override 084 @ParametricNullness 085 public E last() { 086 return delegate().last(); 087 } 088 089 @Override 090 public SortedSet<E> subSet(@ParametricNullness E fromElement, @ParametricNullness E toElement) { 091 return delegate().subSet(fromElement, toElement); 092 } 093 094 @Override 095 public SortedSet<E> tailSet(@ParametricNullness E fromElement) { 096 return delegate().tailSet(fromElement); 097 } 098 099 /** 100 * A sensible definition of {@link #contains} in terms of the {@code first()} method of {@link 101 * #tailSet}. If you override {@link #tailSet}, you may wish to override {@link #contains} to 102 * forward to this implementation. 103 * 104 * @since 7.0 105 */ 106 @Override 107 protected boolean standardContains(@CheckForNull Object object) { 108 try { 109 // any ClassCastExceptions and NullPointerExceptions are caught 110 @SuppressWarnings({"unchecked", "nullness"}) 111 SortedSet<@Nullable Object> self = (SortedSet<@Nullable Object>) this; 112 Object ceiling = self.tailSet(object).first(); 113 return unsafeCompare(comparator(), ceiling, object) == 0; 114 } catch (ClassCastException | NoSuchElementException | NullPointerException e) { 115 return false; 116 } 117 } 118 119 /** 120 * A sensible definition of {@link #remove} in terms of the {@code iterator()} method of {@link 121 * #tailSet}. If you override {@link #tailSet}, you may wish to override {@link #remove} to 122 * forward to this implementation. 123 * 124 * @since 7.0 125 */ 126 @Override 127 protected boolean standardRemove(@CheckForNull Object object) { 128 try { 129 // any ClassCastExceptions and NullPointerExceptions are caught 130 @SuppressWarnings({"unchecked", "nullness"}) 131 SortedSet<@Nullable Object> self = (SortedSet<@Nullable Object>) this; 132 Iterator<?> iterator = self.tailSet(object).iterator(); 133 if (iterator.hasNext()) { 134 Object ceiling = iterator.next(); 135 if (unsafeCompare(comparator(), ceiling, object) == 0) { 136 iterator.remove(); 137 return true; 138 } 139 } 140 } catch (ClassCastException | NullPointerException e) { 141 return false; 142 } 143 return false; 144 } 145 146 /** 147 * A sensible default implementation of {@link #subSet(Object, Object)} in terms of {@link 148 * #headSet(Object)} and {@link #tailSet(Object)}. In some situations, you may wish to override 149 * {@link #subSet(Object, Object)} to forward to this implementation. 150 * 151 * @since 7.0 152 */ 153 protected SortedSet<E> standardSubSet( 154 @ParametricNullness E fromElement, @ParametricNullness E toElement) { 155 return tailSet(fromElement).headSet(toElement); 156 } 157}