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 @Override
064 public Map<C, V> get() {
065 return Maps.newHashMapWithExpectedSize(expectedSize);
066 }
067 private static final long serialVersionUID = 0;
068 }
069
070 /**
071 * Creates an empty {@code HashBasedTable}.
072 */
073 public static <R, C, V> HashBasedTable<R, C, V> create() {
074 return new HashBasedTable<R, C, V>(
075 new HashMap<R, Map<C, V>>(), new Factory<C, V>(0));
076 }
077
078 /**
079 * Creates an empty {@code HashBasedTable} with the specified map sizes.
080 *
081 * @param expectedRows the expected number of distinct row keys
082 * @param expectedCellsPerRow the expected number of column key / value
083 * mappings in each row
084 * @throws IllegalArgumentException if {@code expectedRows} or {@code
085 * expectedCellsPerRow} is negative
086 */
087 public static <R, C, V> HashBasedTable<R, C, V> create(
088 int expectedRows, int expectedCellsPerRow) {
089 checkArgument(expectedCellsPerRow >= 0);
090 Map<R, Map<C, V>> backingMap =
091 Maps.newHashMapWithExpectedSize(expectedRows);
092 return new HashBasedTable<R, C, V>(
093 backingMap, new Factory<C, V>(expectedCellsPerRow));
094 }
095
096 /**
097 * Creates a {@code HashBasedTable} with the same mappings as the specified
098 * table.
099 *
100 * @param table the table to copy
101 * @throws NullPointerException if any of the row keys, column keys, or values
102 * in {@code table} is null
103 */
104 public static <R, C, V> HashBasedTable<R, C, V> create(
105 Table<? extends R, ? extends C, ? extends V> table) {
106 HashBasedTable<R, C, V> result = create();
107 result.putAll(table);
108 return result;
109 }
110
111 HashBasedTable(Map<R, Map<C, V>> backingMap, Factory<C, V> factory) {
112 super(backingMap, factory);
113 }
114
115 // Overriding so NullPointerTester test passes.
116
117 @Override public boolean contains(
118 @Nullable Object rowKey, @Nullable Object columnKey) {
119 return super.contains(rowKey, columnKey);
120 }
121
122 @Override public boolean containsColumn(@Nullable Object columnKey) {
123 return super.containsColumn(columnKey);
124 }
125
126 @Override public boolean containsRow(@Nullable Object rowKey) {
127 return super.containsRow(rowKey);
128 }
129
130 @Override public boolean containsValue(@Nullable Object value) {
131 return super.containsValue(value);
132 }
133
134 @Override public V get(@Nullable Object rowKey, @Nullable Object columnKey) {
135 return super.get(rowKey, columnKey);
136 }
137
138 @Override public boolean equals(@Nullable Object obj) {
139 return super.equals(obj);
140 }
141
142 @Override public V remove(
143 @Nullable Object rowKey, @Nullable Object columnKey) {
144 return super.remove(rowKey, columnKey);
145 }
146
147 private static final long serialVersionUID = 0;
148 }