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
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 com.google.common.base.Supplier;
024
025import java.io.Serializable;
026import java.util.HashMap;
027import java.util.Map;
028
029import javax.annotation.Nullable;
030
031/**
032 * Implementation of {@link Table} using hash tables.
033 *
034 * <p>The views returned by {@link #column}, {@link #columnKeySet()}, and {@link
035 * #columnMap()} have iterators that don't support {@code remove()}. Otherwise,
036 * all optional operations are supported. Null row keys, columns keys, and
037 * values are not supported.
038 *
039 * <p>Lookups by row key are often faster than lookups by column key, because
040 * the data is stored in a {@code Map<R, Map<C, V>>}. A method call like {@code
041 * column(columnKey).get(rowKey)} still runs quickly, since the row key is
042 * provided. However, {@code column(columnKey).size()} takes longer, since an
043 * iteration across all row keys occurs.
044 *
045 * <p>Note that this implementation is not synchronized. If multiple threads
046 * access this table concurrently and one of the threads modifies the table, it
047 * must be synchronized externally.
048 *
049 * @author Jared Levy
050 * @since 7
051 */
052@GwtCompatible(serializable = true)
053@Beta
054public class HashBasedTable<R, C, V> extends StandardTable<R, C, V> {
055  private static class Factory<C, V>
056      implements Supplier<Map<C, V>>, Serializable {
057    final int expectedSize;
058    Factory(int expectedSize) {
059      this.expectedSize = expectedSize;
060    }
061    @Override
062    public Map<C, V> get() {
063      return Maps.newHashMapWithExpectedSize(expectedSize);
064    }
065    private static final long serialVersionUID = 0;
066  }
067
068  /**
069   * Creates an empty {@code HashBasedTable}.
070   */
071  public static <R, C, V> HashBasedTable<R, C, V> create() {
072    return new HashBasedTable<R, C, V>(
073        new HashMap<R, Map<C, V>>(), new Factory<C, V>(0));
074  }
075
076  /**
077   * Creates an empty {@code HashBasedTable} with the specified map sizes.
078   *
079   * @param expectedRows the expected number of distinct row keys
080   * @param expectedCellsPerRow the expected number of column key / value
081   *     mappings in each row
082   * @throws IllegalArgumentException if {@code expectedRows} or {@code
083   *     expectedCellsPerRow} is negative
084   */
085  public static <R, C, V> HashBasedTable<R, C, V> create(
086      int expectedRows, int expectedCellsPerRow) {
087    checkArgument(expectedCellsPerRow >= 0);
088    Map<R, Map<C, V>> backingMap = Maps.newHashMapWithExpectedSize(expectedRows);
089    return new HashBasedTable<R, C, V>(
090        backingMap, new Factory<C, V>(expectedCellsPerRow));
091  }
092
093  /**
094   * Creates a {@code HashBasedTable} with the same mappings as the specified
095   * table.
096   *
097   * @param table the table to copy
098   * @throws NullPointerException if any of the row keys, column keys, or values
099   *     in {@code table} are null.
100   */
101  public static <R, C, V> HashBasedTable<R, C, V> create(
102      Table<? extends R, ? extends C, ? extends V> table) {
103    HashBasedTable<R, C, V> result = create();
104    result.putAll(table);
105    return result;
106  }
107
108  HashBasedTable(Map<R, Map<C, V>> backingMap, Factory<C, V> factory) {
109    super(backingMap, factory);
110  }
111
112  // Overriding so NullPointerTester test passes.
113
114  @Override public boolean contains(
115      @Nullable Object rowKey, @Nullable Object columnKey) {
116    return super.contains(rowKey, columnKey);
117  }
118
119  @Override public boolean containsColumn(@Nullable Object columnKey) {
120    return super.containsColumn(columnKey);
121  }
122
123  @Override public boolean containsRow(@Nullable Object rowKey) {
124    return super.containsRow(rowKey);
125  }
126
127  @Override public boolean containsValue(@Nullable Object value) {
128    return super.containsValue(value);
129  }
130
131  @Override public V get(@Nullable Object rowKey, @Nullable Object columnKey) {
132    return super.get(rowKey, columnKey);
133  }
134
135  @Override public boolean equals(@Nullable Object obj) {
136    return super.equals(obj);
137  }
138
139  @Override public V remove(
140      @Nullable Object rowKey, @Nullable Object columnKey) {
141    return super.remove(rowKey, columnKey);
142  }
143
144  private static final long serialVersionUID = 0;
145}