    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.Beta;
    022    import com.google.common.annotations.GwtCompatible;
    023    import com.google.common.base.Supplier;
    024
    025    import java.io.Serializable;
    026    import java.util.HashMap;
    027    import java.util.Map;
    028
    029    import 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 7.0
    051     */
    052    @GwtCompatible(serializable = true)
    053    @Beta
    054    public 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 =
    089            Maps.newHashMapWithExpectedSize(expectedRows);
    090        return new HashBasedTable<R, C, V>(
    091            backingMap, new Factory<C, V>(expectedCellsPerRow));
    092      }
    093
    094      /**
    095       * Creates a {@code HashBasedTable} with the same mappings as the specified
    096       * table.
    097       *
    098       * @param table the table to copy
    099       * @throws NullPointerException if any of the row keys, column keys, or values
    100       *     in {@code table} is null
    101       */
    102      public static <R, C, V> HashBasedTable<R, C, V> create(
    103          Table<? extends R, ? extends C, ? extends V> table) {
    104        HashBasedTable<R, C, V> result = create();
    105        result.putAll(table);
    106        return result;
    107      }
    108
    109      HashBasedTable(Map<R, Map<C, V>> backingMap, Factory<C, V> factory) {
    110        super(backingMap, factory);
    111      }
    112
    113      // Overriding so NullPointerTester test passes.
    114
    115      @Override public boolean contains(
    116          @Nullable Object rowKey, @Nullable Object columnKey) {
    117        return super.contains(rowKey, columnKey);
    118      }
    119
    120      @Override public boolean containsColumn(@Nullable Object columnKey) {
    121        return super.containsColumn(columnKey);
    122      }
    123
    124      @Override public boolean containsRow(@Nullable Object rowKey) {
    125        return super.containsRow(rowKey);
    126      }
    127
    128      @Override public boolean containsValue(@Nullable Object value) {
    129        return super.containsValue(value);
    130      }
    131
    132      @Override public V get(@Nullable Object rowKey, @Nullable Object columnKey) {
    133        return super.get(rowKey, columnKey);
    134      }
    135
    136      @Override public boolean equals(@Nullable Object obj) {
    137        return super.equals(obj);
    138      }
    139
    140      @Override public V remove(
    141          @Nullable Object rowKey, @Nullable Object columnKey) {
    142        return super.remove(rowKey, columnKey);
    143      }
    144
    145      private static final long serialVersionUID = 0;
    146    }