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.base.Preconditions.checkArgument; 020 021import com.google.common.annotations.Beta; 022import com.google.common.annotations.GwtCompatible; 023import java.util.Comparator; 024import java.util.NoSuchElementException; 025import java.util.SortedMap; 026import org.checkerframework.checker.nullness.qual.Nullable; 027 028/** 029 * A sorted map which forwards all its method calls to another sorted map. Subclasses should 030 * override one or more methods to modify the behavior of the backing sorted map as desired per the 031 * <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>. 032 * 033 * <p><b>Warning:</b> The methods of {@code ForwardingSortedMap} forward <i>indiscriminately</i> to 034 * the methods of the delegate. For example, overriding {@link #put} alone <i>will not</i> change 035 * the behavior of {@link #putAll}, which can lead to unexpected behavior. In this case, you should 036 * override {@code putAll} as well, either providing your own implementation, or delegating to the 037 * provided {@code standardPutAll} method. 038 * 039 * <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code 040 * default} methods. Instead, it inherits their default implementations. When those implementations 041 * invoke methods, they invoke methods on the {@code ForwardingSortedMap}. 042 * 043 * <p>Each of the {@code standard} methods, where appropriate, use the comparator of the map to test 044 * equality for both keys and values, unlike {@code ForwardingMap}. 045 * 046 * <p>The {@code standard} methods and the collection views they return are not guaranteed to be 047 * thread-safe, even when all of the methods that they depend on are thread-safe. 048 * 049 * @author Mike Bostock 050 * @author Louis Wasserman 051 * @since 2.0 052 */ 053@GwtCompatible 054public abstract class ForwardingSortedMap<K, V> extends ForwardingMap<K, V> 055 implements SortedMap<K, V> { 056 // TODO(lowasser): identify places where thread safety is actually lost 057 058 /** Constructor for use by subclasses. */ 059 protected ForwardingSortedMap() {} 060 061 @Override 062 protected abstract SortedMap<K, V> delegate(); 063 064 @Override 065 public Comparator<? super K> comparator() { 066 return delegate().comparator(); 067 } 068 069 @Override 070 public K firstKey() { 071 return delegate().firstKey(); 072 } 073 074 @Override 075 public SortedMap<K, V> headMap(K toKey) { 076 return delegate().headMap(toKey); 077 } 078 079 @Override 080 public K lastKey() { 081 return delegate().lastKey(); 082 } 083 084 @Override 085 public SortedMap<K, V> subMap(K fromKey, K toKey) { 086 return delegate().subMap(fromKey, toKey); 087 } 088 089 @Override 090 public SortedMap<K, V> tailMap(K fromKey) { 091 return delegate().tailMap(fromKey); 092 } 093 094 /** 095 * A sensible implementation of {@link SortedMap#keySet} in terms of the methods of {@code 096 * ForwardingSortedMap}. In many cases, you may wish to override {@link 097 * ForwardingSortedMap#keySet} to forward to this implementation or a subclass thereof. 098 * 099 * @since 15.0 100 */ 101 @Beta 102 protected class StandardKeySet extends Maps.SortedKeySet<K, V> { 103 /** Constructor for use by subclasses. */ 104 public StandardKeySet() { 105 super(ForwardingSortedMap.this); 106 } 107 } 108 109 // unsafe, but worst case is a CCE is thrown, which callers will be expecting 110 @SuppressWarnings("unchecked") 111 private int unsafeCompare(Object k1, Object k2) { 112 Comparator<? super K> comparator = comparator(); 113 if (comparator == null) { 114 return ((Comparable<Object>) k1).compareTo(k2); 115 } else { 116 return ((Comparator<Object>) comparator).compare(k1, k2); 117 } 118 } 119 120 /** 121 * A sensible definition of {@link #containsKey} in terms of the {@code firstKey()} method of 122 * {@link #tailMap}. If you override {@link #tailMap}, you may wish to override {@link 123 * #containsKey} to forward to this implementation. 124 * 125 * @since 7.0 126 */ 127 @Override 128 @Beta 129 protected boolean standardContainsKey(@Nullable Object key) { 130 try { 131 // any CCE will be caught 132 @SuppressWarnings("unchecked") 133 SortedMap<Object, V> self = (SortedMap<Object, V>) this; 134 Object ceilingKey = self.tailMap(key).firstKey(); 135 return unsafeCompare(ceilingKey, key) == 0; 136 } catch (ClassCastException | NoSuchElementException | NullPointerException e) { 137 return false; 138 } 139 } 140 141 /** 142 * A sensible default implementation of {@link #subMap(Object, Object)} in terms of {@link 143 * #headMap(Object)} and {@link #tailMap(Object)}. In some situations, you may wish to override 144 * {@link #subMap(Object, Object)} to forward to this implementation. 145 * 146 * @since 7.0 147 */ 148 @Beta 149 protected SortedMap<K, V> standardSubMap(K fromKey, K toKey) { 150 checkArgument(unsafeCompare(fromKey, toKey) <= 0, "fromKey must be <= toKey"); 151 return tailMap(fromKey).headMap(toKey); 152 } 153}