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 */ 016 017 package com.google.common.collect; 018 019 import com.google.common.annotations.Beta; 020 import com.google.common.annotations.GwtCompatible; 021 022 import java.util.Comparator; 023 import java.util.Iterator; 024 import java.util.NoSuchElementException; 025 import java.util.SortedSet; 026 027 import javax.annotation.Nullable; 028 029 /** 030 * A sorted set which forwards all its method calls to another sorted set. 031 * Subclasses should override one or more methods to modify the behavior of the 032 * backing sorted set as desired per the <a 033 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>. 034 * 035 * <p><em>Warning</em>: The methods of {@code ForwardingSortedSet} forward 036 * <em>indiscriminately</em> to the methods of the delegate. For example, 037 * overriding {@link #add} alone <em>will not</em> change the behavior of {@link 038 * #addAll}, which can lead to unexpected behavior. In this case, you should 039 * override {@code addAll} as well, either providing your own implementation, or 040 * delegating to the provided {@code standardAddAll} method. 041 * 042 * <p>Each of the {@code standard} methods, where appropriate, uses the set's 043 * comparator (or the natural ordering of the elements, if there is no 044 * comparator) to test element equality. As a result, if the comparator is not 045 * consistent with equals, some of the standard implementations may violate the 046 * {@code Set} contract. 047 * 048 * <p>The {@code standard} methods and the collection views they return are not 049 * guaranteed to be thread-safe, even when all of the methods that they depend 050 * on are thread-safe. 051 * 052 * @author Mike Bostock 053 * @author Louis Wasserman 054 * @since 2 (imported from Google Collections Library) 055 */ 056 @GwtCompatible 057 public abstract class ForwardingSortedSet<E> extends ForwardingSet<E> 058 implements SortedSet<E> { 059 060 /** Constructor for use by subclasses. */ 061 protected ForwardingSortedSet() {} 062 063 @Override protected abstract SortedSet<E> delegate(); 064 065 @Override 066 public Comparator<? super E> comparator() { 067 return delegate().comparator(); 068 } 069 070 @Override 071 public E first() { 072 return delegate().first(); 073 } 074 075 @Override 076 public SortedSet<E> headSet(E toElement) { 077 return delegate().headSet(toElement); 078 } 079 080 @Override 081 public E last() { 082 return delegate().last(); 083 } 084 085 @Override 086 public SortedSet<E> subSet(E fromElement, E toElement) { 087 return delegate().subSet(fromElement, toElement); 088 } 089 090 @Override 091 public SortedSet<E> tailSet(E fromElement) { 092 return delegate().tailSet(fromElement); 093 } 094 095 // unsafe, but worst case is a CCE is thrown, which callers will be expecting 096 @SuppressWarnings("unchecked") 097 private int unsafeCompare(Object o1, Object o2) { 098 Comparator<? super E> comparator = comparator(); 099 return (comparator == null) 100 ? ((Comparable<Object>) o1).compareTo(o2) 101 : ((Comparator<Object>) comparator).compare(o1, o2); 102 } 103 104 /** 105 * A sensible definition of {@link #contains} in terms of the {@code first()} 106 * method of {@link #tailSet}. If you override {@link #tailSet}, you may wish 107 * to override {@link #contains} to forward to this implementation. 108 * 109 * @since 7 110 */ 111 @Override @Beta protected boolean standardContains(@Nullable Object object) { 112 try { 113 // any ClassCastExceptions are caught 114 @SuppressWarnings("unchecked") 115 SortedSet<Object> self = (SortedSet<Object>) this; 116 Object ceiling = self.tailSet(object).first(); 117 return unsafeCompare(ceiling, object) == 0; 118 } catch (ClassCastException e) { 119 return false; 120 } catch (NoSuchElementException e) { 121 return false; 122 } catch (NullPointerException e) { 123 return false; 124 } 125 } 126 127 /** 128 * A sensible definition of {@link #remove} in terms of the {@code iterator()} 129 * method of {@link #tailSet}. If you override {@link #tailSet}, you may wish 130 * to override {@link #remove} to forward to this implementation. 131 * 132 * @since 7 133 */ 134 @Override @Beta protected boolean standardRemove(@Nullable Object object) { 135 try { 136 // any ClassCastExceptions are caught 137 @SuppressWarnings("unchecked") 138 SortedSet<Object> self = (SortedSet<Object>) this; 139 Iterator<Object> iterator = self.tailSet(object).iterator(); 140 if (iterator.hasNext()) { 141 Object ceiling = iterator.next(); 142 if (unsafeCompare(ceiling, object) == 0) { 143 iterator.remove(); 144 return true; 145 } 146 } 147 } catch (ClassCastException e) { 148 return false; 149 } catch (NullPointerException e) { 150 return false; 151 } 152 return false; 153 } 154 155 /** 156 * A sensible default implementation of {@link #subSet(Object, Object)} in 157 * terms of {@link #headSet(Object)} and {@link #tailSet(Object)}. In some 158 * situations, you may wish to override {@link #subSet(Object, Object)} to 159 * forward to this implementation. 160 * 161 * @since 7 162 */ 163 @Beta protected SortedSet<E> standardSubSet(E fromElement, E toElement) { 164 return tailSet(fromElement).headSet(toElement); 165 } 166 }