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 javax.annotation.CheckForNull; 027import org.checkerframework.checker.nullness.qual.Nullable; 028 029/** 030 * A sorted map which forwards all its method calls to another sorted map. Subclasses should 031 * override one or more methods to modify the behavior of the backing sorted map 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 ForwardingSortedMap} forward <i>indiscriminately</i> to 035 * the methods of the delegate. For example, overriding {@link #put} alone <i>will not</i> change 036 * the behavior of {@link #putAll}, which can lead to unexpected behavior. In this case, you should 037 * override {@code putAll} as well, either providing your own implementation, or delegating to the 038 * provided {@code standardPutAll} 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 ForwardingSortedMap}. 043 * 044 * <p>Each of the {@code standard} methods, where appropriate, use the comparator of the map to test 045 * equality for both keys and values, unlike {@code ForwardingMap}. 046 * 047 * <p>The {@code standard} methods and the collection views they return are not guaranteed to be 048 * thread-safe, even when all of the methods that they depend on are thread-safe. 049 * 050 * @author Mike Bostock 051 * @author Louis Wasserman 052 * @since 2.0 053 */ 054@GwtCompatible 055@ElementTypesAreNonnullByDefault 056public abstract class ForwardingSortedMap<K extends @Nullable Object, V extends @Nullable Object> 057 extends ForwardingMap<K, V> implements SortedMap<K, V> { 058 // TODO(lowasser): identify places where thread safety is actually lost 059 060 /** Constructor for use by subclasses. */ 061 protected ForwardingSortedMap() {} 062 063 @Override 064 protected abstract SortedMap<K, V> delegate(); 065 066 @Override 067 @CheckForNull 068 public Comparator<? super K> comparator() { 069 return delegate().comparator(); 070 } 071 072 @Override 073 @ParametricNullness 074 public K firstKey() { 075 return delegate().firstKey(); 076 } 077 078 @Override 079 public SortedMap<K, V> headMap(@ParametricNullness K toKey) { 080 return delegate().headMap(toKey); 081 } 082 083 @Override 084 @ParametricNullness 085 public K lastKey() { 086 return delegate().lastKey(); 087 } 088 089 @Override 090 public SortedMap<K, V> subMap(@ParametricNullness K fromKey, @ParametricNullness K toKey) { 091 return delegate().subMap(fromKey, toKey); 092 } 093 094 @Override 095 public SortedMap<K, V> tailMap(@ParametricNullness K fromKey) { 096 return delegate().tailMap(fromKey); 097 } 098 099 /** 100 * A sensible implementation of {@link SortedMap#keySet} in terms of the methods of {@code 101 * ForwardingSortedMap}. In many cases, you may wish to override {@link 102 * ForwardingSortedMap#keySet} to forward to this implementation or a subclass thereof. 103 * 104 * @since 15.0 105 */ 106 @Beta 107 protected class StandardKeySet extends Maps.SortedKeySet<K, V> { 108 /** Constructor for use by subclasses. */ 109 public StandardKeySet() { 110 super(ForwardingSortedMap.this); 111 } 112 } 113 114 // unsafe, but worst case is a CCE or NPE is thrown, which callers will be expecting 115 @SuppressWarnings({"unchecked", "nullness"}) 116 static int unsafeCompare( 117 @CheckForNull Comparator<?> comparator, @CheckForNull Object o1, @CheckForNull Object o2) { 118 if (comparator == null) { 119 return ((Comparable<@Nullable Object>) o1).compareTo(o2); 120 } else { 121 return ((Comparator<@Nullable Object>) comparator).compare(o1, o2); 122 } 123 } 124 125 /** 126 * A sensible definition of {@link #containsKey} in terms of the {@code firstKey()} method of 127 * {@link #tailMap}. If you override {@link #tailMap}, you may wish to override {@link 128 * #containsKey} to forward to this implementation. 129 * 130 * @since 7.0 131 */ 132 @Override 133 @Beta 134 protected boolean standardContainsKey(@CheckForNull Object key) { 135 try { 136 // any CCE or NPE will be caught 137 @SuppressWarnings({"unchecked", "nullness"}) 138 SortedMap<@Nullable Object, V> self = (SortedMap<@Nullable Object, V>) this; 139 Object ceilingKey = self.tailMap(key).firstKey(); 140 return unsafeCompare(comparator(), ceilingKey, key) == 0; 141 } catch (ClassCastException | NoSuchElementException | NullPointerException e) { 142 return false; 143 } 144 } 145 146 /** 147 * A sensible default implementation of {@link #subMap(Object, Object)} in terms of {@link 148 * #headMap(Object)} and {@link #tailMap(Object)}. In some situations, you may wish to override 149 * {@link #subMap(Object, Object)} to forward to this implementation. 150 * 151 * @since 7.0 152 */ 153 @Beta 154 protected SortedMap<K, V> standardSubMap(K fromKey, K toKey) { 155 checkArgument(unsafeCompare(comparator(), fromKey, toKey) <= 0, "fromKey must be <= toKey"); 156 return tailMap(fromKey).headMap(toKey); 157 } 158}