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Java example source code file (HashBasedTable.java)

This example Java source code file (HashBasedTable.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

annotation, canignorereturnvalue, factory, gwtcompatible, hashbasedtable, hashmap, map, nullable, object, override, serializable, standardtable, util

The HashBasedTable.java Java example source code

/*
 * 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 com.google.errorprone.annotations.CanIgnoreReturnValue;

import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;

import javax.annotation.Nullable;

/**
 * Implementation of {@link Table} using hash tables.
 *
 * <p>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.
 *
 * <p>Lookups by row key are often faster than lookups by column key, because
 * the data is stored in a {@code Map<R, 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.
 *
 * <p>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.
 *
 * <p>See the Guava User Guide article on  {
  private static class Factory<C, V> implements Supplier>, Serializable {
    final int expectedSize;

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

    @Override
    public Map<C, V> get() {
      return Maps.newHashMapWithExpectedSize(expectedSize);
    }

    private static final long serialVersionUID = 0;
  }

  /**
   * Creates an empty {@code HashBasedTable}.
   */
  public static <R, C, V> HashBasedTable create() {
    return new HashBasedTable<R, C, V>(new HashMap>(), 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 <R, C, V> HashBasedTable create(
      int expectedRows, int expectedCellsPerRow) {
    checkNonnegative(expectedCellsPerRow, "expectedCellsPerRow");
    Map<R, Map backingMap = Maps.newHashMapWithExpectedSize(expectedRows);
    return new HashBasedTable<R, C, V>(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 <R, C, V> HashBasedTable create(
      Table<? extends R, ? extends C, ? extends V> table) {
    HashBasedTable<R, C, V> result = create();
    result.putAll(table);
    return result;
  }

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

  // Overriding so NullPointerTester test passes.

  @Override
  public boolean contains(@Nullable Object rowKey, @Nullable Object columnKey) {
    return super.contains(rowKey, columnKey);
  }

  @Override
  public boolean containsColumn(@Nullable Object columnKey) {
    return super.containsColumn(columnKey);
  }

  @Override
  public boolean containsRow(@Nullable Object rowKey) {
    return super.containsRow(rowKey);
  }

  @Override
  public boolean containsValue(@Nullable Object value) {
    return super.containsValue(value);
  }

  @Override
  public V get(@Nullable Object rowKey, @Nullable Object columnKey) {
    return super.get(rowKey, columnKey);
  }

  @Override
  public boolean equals(@Nullable Object obj) {
    return super.equals(obj);
  }

  @CanIgnoreReturnValue
  @Override
  public V remove(@Nullable Object rowKey, @Nullable Object columnKey) {
    return super.remove(rowKey, columnKey);
  }

  private static final long serialVersionUID = 0;
}
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