com.google.common.collect.HashBasedTable Maven / Gradle / Ivy

/*
 * Copyright (C) 2008 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import static com.google.common.collect.CollectPreconditions.checkNonnegative;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Supplier;
import java.io.Serializable;
import java.util.LinkedHashMap;
import java.util.Map;

/**
 * Implementation of {@link Table} using linked hash tables. This guarantees predictable iteration
 * order of the various views.
 *
 * The views returned by {@link #column}, {@link #columnKeySet()}, and {@link #columnMap()} have
 * iterators that don't support {@code remove()}. Otherwise, all optional operations are supported.
 * Null row keys, columns keys, and values are not supported.
 *
 * 
Lookups by row key are often faster than lookups by column key, because the data is stored in
 * a {@code Map>}. A method call like {@code column(columnKey).get(rowKey)} still runs
 * quickly, since the row key is provided. However, {@code column(columnKey).size()} takes longer,
 * since an iteration across all row keys occurs.
 *
 * 
Note that this implementation is not synchronized. If multiple threads access this table
 * concurrently and one of the threads modifies the table, it must be synchronized externally.
 *
 * See the Guava User Guide article on {@code Table}.
 *
 * @author Jared Levy
 * @since 7.0
 */
@GwtCompatible(serializable = true)
@ElementTypesAreNonnullByDefault
public class HashBasedTable extends StandardTable {
  private static class Factory implements Supplier>, Serializable {
    final int expectedSize;

    Factory(int expectedSize) {
      this.expectedSize = expectedSize;
    }

    @Override
    public Map get() {
      return Maps.newLinkedHashMapWithExpectedSize(expectedSize);
    }

    private static final long serialVersionUID = 0;
  }

  /** Creates an empty {@code HashBasedTable}. */
  public static  HashBasedTable create() {
    return new HashBasedTable<>(new LinkedHashMap>(), new Factory(0));
  }

  /**
   * Creates an empty {@code HashBasedTable} with the specified map sizes.
   *
   * @param expectedRows the expected number of distinct row keys
   * @param expectedCellsPerRow the expected number of column key / value mappings in each row
   * @throws IllegalArgumentException if {@code expectedRows} or {@code expectedCellsPerRow} is
   *     negative
   */
  public static  HashBasedTable create(
      int expectedRows, int expectedCellsPerRow) {
    checkNonnegative(expectedCellsPerRow, "expectedCellsPerRow");
    Map> backingMap = Maps.newLinkedHashMapWithExpectedSize(expectedRows);
    return new HashBasedTable<>(backingMap, new Factory(expectedCellsPerRow));
  }

  /**
   * Creates a {@code HashBasedTable} with the same mappings as the specified table.
   *
   * @param table the table to copy
   * @throws NullPointerException if any of the row keys, column keys, or values in {@code table} is
   *     null
   */
  public static  HashBasedTable create(
      Table table) {
    HashBasedTable result = create();
    result.putAll(table);
    return result;
  }

  HashBasedTable(Map> backingMap, Factory factory) {
    super(backingMap, factory);
  }

  private static final long serialVersionUID = 0;
}