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.Comparator; 23 import java.util.Iterator; 24 import java.util.NoSuchElementException; 25 import java.util.SortedSet; 26 27 import javax.annotation.Nullable; 28 29 /** 30 * A sorted set which forwards all its method calls to another sorted set. 31 * Subclasses should override one or more methods to modify the behavior of the 32 * backing sorted set as desired per the <a 33 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>. 34 * 35 * <p><i>Warning:</i> The methods of {@code ForwardingSortedSet} forward 36 * <i>indiscriminately</i> to the methods of the delegate. For example, 37 * overriding {@link #add} alone <i>will not</i> change the behavior of {@link 38 * #addAll}, which can lead to unexpected behavior. In this case, you should 39 * override {@code addAll} as well, either providing your own implementation, or 40 * delegating to the provided {@code standardAddAll} method. 41 * 42 * <p>Each of the {@code standard} methods, where appropriate, uses the set's 43 * comparator (or the natural ordering of the elements, if there is no 44 * comparator) to test element equality. As a result, if the comparator is not 45 * consistent with equals, some of the standard implementations may violate the 46 * {@code Set} contract. 47 * 48 * <p>The {@code standard} methods and the collection views they return are not 49 * guaranteed to be thread-safe, even when all of the methods that they depend 50 * on are thread-safe. 51 * 52 * @author Mike Bostock 53 * @author Louis Wasserman 54 * @since 2.0 (imported from Google Collections Library) 55 */ 56 @GwtCompatible 57 public abstract class ForwardingSortedSet<E> extends ForwardingSet<E> 58 implements SortedSet<E> { 59 60 /** Constructor for use by subclasses. */ 61 protected ForwardingSortedSet() {} 62 63 @Override protected abstract SortedSet<E> delegate(); 64 65 @Override 66 public Comparator<? super E> comparator() { 67 return delegate().comparator(); 68 } 69 70 @Override 71 public E first() { 72 return delegate().first(); 73 } 74 75 @Override 76 public SortedSet<E> headSet(E toElement) { 77 return delegate().headSet(toElement); 78 } 79 80 @Override 81 public E last() { 82 return delegate().last(); 83 } 84 85 @Override 86 public SortedSet<E> subSet(E fromElement, E toElement) { 87 return delegate().subSet(fromElement, toElement); 88 } 89 90 @Override 91 public SortedSet<E> tailSet(E fromElement) { 92 return delegate().tailSet(fromElement); 93 } 94 95 // unsafe, but worst case is a CCE is thrown, which callers will be expecting 96 @SuppressWarnings("unchecked") 97 private int unsafeCompare(Object o1, Object o2) { 98 Comparator<? super E> comparator = comparator(); 99 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 7.0 110 */ 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 7.0 133 */ 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 7.0 162 */ 163 @Beta protected SortedSet<E> standardSubSet(E fromElement, E toElement) { 164 return tailSet(fromElement).headSet(toElement); 165 } 166 } 167
