001 /*
002 * Copyright (C) 2008 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 static com.google.common.base.Preconditions.checkArgument;
020
021 import com.google.common.annotations.GwtCompatible;
022 import com.google.common.base.Supplier;
023
024 import java.io.Serializable;
025 import java.util.HashMap;
026 import java.util.Map;
027
028 import javax.annotation.Nullable;
029
030 /**
031 * Implementation of {@link Table} using hash tables.
032 *
033 * <p>The views returned by {@link #column}, {@link #columnKeySet()}, and {@link
034 * #columnMap()} have iterators that don't support {@code remove()}. Otherwise,
035 * all optional operations are supported. Null row keys, columns keys, and
036 * values are not supported.
037 *
038 * <p>Lookups by row key are often faster than lookups by column key, because
039 * the data is stored in a {@code Map<R, Map<C, V>>}. A method call like {@code
040 * column(columnKey).get(rowKey)} still runs quickly, since the row key is
041 * provided. However, {@code column(columnKey).size()} takes longer, since an
042 * iteration across all row keys occurs.
043 *
044 * <p>Note that this implementation is not synchronized. If multiple threads
045 * access this table concurrently and one of the threads modifies the table, it
046 * must be synchronized externally.
047 *
048 * <p>See the Guava User Guide article on <a href=
049 * "http://code.google.com/p/guava-libraries/wiki/NewCollectionTypesExplained#Table">
050 * {@code Table}</a>.
051 *
052 * @author Jared Levy
053 * @since 7.0
054 */
055 @GwtCompatible(serializable = true)
056 public class HashBasedTable<R, C, V> extends StandardTable<R, C, V> {
057 private static class Factory<C, V>
058 implements Supplier<Map<C, V>>, Serializable {
059 final int expectedSize;
060 Factory(int expectedSize) {
061 this.expectedSize = expectedSize;
062 }
063 public Map<C, V> get() {
064 return Maps.newHashMapWithExpectedSize(expectedSize);
065 }
066 private static final long serialVersionUID = 0;
067 }
068
069 /**
070 * Creates an empty {@code HashBasedTable}.
071 */
072 public static <R, C, V> HashBasedTable<R, C, V> create() {
073 return new HashBasedTable<R, C, V>(
074 new HashMap<R, Map<C, V>>(), new Factory<C, V>(0));
075 }
076
077 /**
078 * Creates an empty {@code HashBasedTable} with the specified map sizes.
079 *
080 * @param expectedRows the expected number of distinct row keys
081 * @param expectedCellsPerRow the expected number of column key / value
082 * mappings in each row
083 * @throws IllegalArgumentException if {@code expectedRows} or {@code
084 * expectedCellsPerRow} is negative
085 */
086 public static <R, C, V> HashBasedTable<R, C, V> create(
087 int expectedRows, int expectedCellsPerRow) {
088 checkArgument(expectedCellsPerRow >= 0);
089 Map<R, Map<C, V>> backingMap =
090 Maps.newHashMapWithExpectedSize(expectedRows);
091 return new HashBasedTable<R, C, V>(
092 backingMap, new Factory<C, V>(expectedCellsPerRow));
093 }
094
095 /**
096 * Creates a {@code HashBasedTable} with the same mappings as the specified
097 * table.
098 *
099 * @param table the table to copy
100 * @throws NullPointerException if any of the row keys, column keys, or values
101 * in {@code table} is null
102 */
103 public static <R, C, V> HashBasedTable<R, C, V> create(
104 Table<? extends R, ? extends C, ? extends V> table) {
105 HashBasedTable<R, C, V> result = create();
106 result.putAll(table);
107 return result;
108 }
109
110 HashBasedTable(Map<R, Map<C, V>> backingMap, Factory<C, V> factory) {
111 super(backingMap, factory);
112 }
113
114 // Overriding so NullPointerTester test passes.
115
116
117 @Override
118 public boolean contains(
119 @Nullable Object rowKey, @Nullable Object columnKey) {
120 return super.contains(rowKey, columnKey);
121 }
122
123
124 @Override
125 public boolean containsColumn(@Nullable Object columnKey) {
126 return super.containsColumn(columnKey);
127 }
128
129
130 @Override
131 public boolean containsRow(@Nullable Object rowKey) {
132 return super.containsRow(rowKey);
133 }
134
135
136 @Override
137 public boolean containsValue(@Nullable Object value) {
138 return super.containsValue(value);
139 }
140
141
142 @Override
143 public V get(@Nullable Object rowKey, @Nullable Object columnKey) {
144 return super.get(rowKey, columnKey);
145 }
146
147
148 @Override
149 public boolean equals(@Nullable Object obj) {
150 return super.equals(obj);
151 }
152
153
154 @Override
155 public V remove(
156 @Nullable Object rowKey, @Nullable Object columnKey) {
157 return super.remove(rowKey, columnKey);
158 }
159
160 private static final long serialVersionUID = 0;
161 }