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;
}