    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    }