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.base.Preconditions.checkArgument;
import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Supplier;
import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;
import javax.annotation.Nullable;
/**
* Implementation of {@link Table} using hash tables.
*
* 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)
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.newHashMapWithExpectedSize(expectedSize);
}
private static final long serialVersionUID = 0;
}
/**
* Creates an empty {@code HashBasedTable}.
*/
public static HashBasedTable create() {
return new HashBasedTable(
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 HashBasedTable create(
int expectedRows, int expectedCellsPerRow) {
checkArgument(expectedCellsPerRow >= 0);
Map> backingMap =
Maps.newHashMapWithExpectedSize(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);
}
// 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);
}
@Override public V remove(
@Nullable Object rowKey, @Nullable Object columnKey) {
return super.remove(rowKey, columnKey);
}
private static final long serialVersionUID = 0;
}