com.google.common.collect.MultimapBuilder Maven / Gradle / Ivy
/*
* Copyright (C) 2013 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.checkNotNull;
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.ArrayList;
import java.util.Collection;
import java.util.Comparator;
import java.util.EnumMap;
import java.util.EnumSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.SortedSet;
import java.util.TreeMap;
import java.util.TreeSet;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* A builder for a multimap implementation that allows customization of the backing map and value
* collection implementations used in a particular multimap.
*
* This can be used to easily configure multimap data structure implementations not provided
* explicitly in {@code com.google.common.collect}, for example:
*
*
{@code
* ListMultimap treeListMultimap =
* MultimapBuilder.treeKeys().arrayListValues().build();
* SetMultimap hashEnumMultimap =
* MultimapBuilder.hashKeys().enumSetValues(MyEnum.class).build();
* }
*
* {@code MultimapBuilder} instances are immutable. Invoking a configuration method has no effect
* on the receiving instance; you must store and use the new builder instance it returns instead.
*
*
The generated multimaps are serializable if the key and value types are serializable, unless
* stated otherwise in one of the configuration methods.
*
* @author Louis Wasserman
* @param An upper bound on the key type of the generated multimap.
* @param An upper bound on the value type of the generated multimap.
* @since 16.0
*/
@GwtCompatible
@ElementTypesAreNonnullByDefault
public abstract class MultimapBuilder {
/*
* Leaving K and V as upper bounds rather than the actual key and value types allows type
* parameters to be left implicit more often. CacheBuilder uses the same technique.
*/
private MultimapBuilder() {}
private static final int DEFAULT_EXPECTED_KEYS = 8;
/** Uses a hash table to map keys to value collections. */
public static MultimapBuilderWithKeys<@Nullable Object> hashKeys() {
return hashKeys(DEFAULT_EXPECTED_KEYS);
}
/**
* Uses a hash table to map keys to value collections, initialized to expect the specified number
* of keys.
*
* @throws IllegalArgumentException if {@code expectedKeys < 0}
*/
public static MultimapBuilderWithKeys<@Nullable Object> hashKeys(int expectedKeys) {
checkNonnegative(expectedKeys, "expectedKeys");
return new MultimapBuilderWithKeys<@Nullable Object>() {
@Override
Map> createMap() {
return Platform.newHashMapWithExpectedSize(expectedKeys);
}
};
}
/**
* Uses a hash table to map keys to value collections.
*
* The collections returned by {@link Multimap#keySet()}, {@link Multimap#keys()}, and {@link
* Multimap#asMap()} will iterate through the keys in the order that they were first added to the
* multimap, save that if all values associated with a key are removed and then the key is added
* back into the multimap, that key will come last in the key iteration order.
*/
public static MultimapBuilderWithKeys<@Nullable Object> linkedHashKeys() {
return linkedHashKeys(DEFAULT_EXPECTED_KEYS);
}
/**
* Uses an hash table to map keys to value collections, initialized to expect the specified number
* of keys.
*
*
The collections returned by {@link Multimap#keySet()}, {@link Multimap#keys()}, and {@link
* Multimap#asMap()} will iterate through the keys in the order that they were first added to the
* multimap, save that if all values associated with a key are removed and then the key is added
* back into the multimap, that key will come last in the key iteration order.
*/
public static MultimapBuilderWithKeys<@Nullable Object> linkedHashKeys(int expectedKeys) {
checkNonnegative(expectedKeys, "expectedKeys");
return new MultimapBuilderWithKeys<@Nullable Object>() {
@Override
Map> createMap() {
return Platform.newLinkedHashMapWithExpectedSize(expectedKeys);
}
};
}
/**
* Uses a naturally-ordered {@link TreeMap} to map keys to value collections.
*
* The collections returned by {@link Multimap#keySet()}, {@link Multimap#keys()}, and {@link
* Multimap#asMap()} will iterate through the keys in sorted order.
*
*
For all multimaps generated by the resulting builder, the {@link Multimap#keySet()} can be
* safely cast to a {@link java.util.SortedSet}, and the {@link Multimap#asMap()} can safely be
* cast to a {@link java.util.SortedMap}.
*/
@SuppressWarnings("rawtypes")
public static MultimapBuilderWithKeys treeKeys() {
return treeKeys(Ordering.natural());
}
/**
* Uses a {@link TreeMap} sorted by the specified comparator to map keys to value collections.
*
* The collections returned by {@link Multimap#keySet()}, {@link Multimap#keys()}, and {@link
* Multimap#asMap()} will iterate through the keys in sorted order.
*
*
For all multimaps generated by the resulting builder, the {@link Multimap#keySet()} can be
* safely cast to a {@link java.util.SortedSet}, and the {@link Multimap#asMap()} can safely be
* cast to a {@link java.util.SortedMap}.
*
*
Multimaps generated by the resulting builder will not be serializable if {@code comparator}
* is not serializable.
*/
public static MultimapBuilderWithKeys treeKeys(
Comparator comparator) {
checkNotNull(comparator);
return new MultimapBuilderWithKeys() {
@Override
Map> createMap() {
return new TreeMap<>(comparator);
}
};
}
/**
* Uses an {@link EnumMap} to map keys to value collections.
*
* @since 16.0
*/
public static > MultimapBuilderWithKeys enumKeys(Class keyClass) {
checkNotNull(keyClass);
return new MultimapBuilderWithKeys() {
@SuppressWarnings("unchecked")
@Override
Map> createMap() {
// K must actually be K0, since enums are effectively final
// (their subclasses are inaccessible)
return (Map>) new EnumMap>(keyClass);
}
};
}
private static final class ArrayListSupplier
implements Supplier>, Serializable {
private final int expectedValuesPerKey;
ArrayListSupplier(int expectedValuesPerKey) {
this.expectedValuesPerKey = checkNonnegative(expectedValuesPerKey, "expectedValuesPerKey");
}
@Override
public List get() {
return new ArrayList<>(expectedValuesPerKey);
}
}
private enum LinkedListSupplier implements Supplier> {
INSTANCE;
public static Supplier> instance() {
// Each call generates a fresh LinkedList, which can serve as a List for any V.
@SuppressWarnings({"rawtypes", "unchecked"})
Supplier> result = (Supplier) INSTANCE;
return result;
}
@Override
public List get() {
return new LinkedList<>();
}
}
private static final class HashSetSupplier
implements Supplier>, Serializable {
private final int expectedValuesPerKey;
HashSetSupplier(int expectedValuesPerKey) {
this.expectedValuesPerKey = checkNonnegative(expectedValuesPerKey, "expectedValuesPerKey");
}
@Override
public Set get() {
return Platform.newHashSetWithExpectedSize(expectedValuesPerKey);
}
}
private static final class LinkedHashSetSupplier
implements Supplier>, Serializable {
private final int expectedValuesPerKey;
LinkedHashSetSupplier(int expectedValuesPerKey) {
this.expectedValuesPerKey = checkNonnegative(expectedValuesPerKey, "expectedValuesPerKey");
}
@Override
public Set get() {
return Platform.newLinkedHashSetWithExpectedSize(expectedValuesPerKey);
}
}
private static final class TreeSetSupplier
implements Supplier>, Serializable {
private final Comparator comparator;
TreeSetSupplier(Comparator comparator) {
this.comparator = checkNotNull(comparator);
}
@Override
public SortedSet get() {
return new TreeSet<>(comparator);
}
}
private static final class EnumSetSupplier>
implements Supplier>, Serializable {
private final Class clazz;
EnumSetSupplier(Class clazz) {
this.clazz = checkNotNull(clazz);
}
@Override
public Set get() {
return EnumSet.noneOf(clazz);
}
}
/**
* An intermediate stage in a {@link MultimapBuilder} in which the key-value collection map
* implementation has been specified, but the value collection implementation has not.
*
* @param The upper bound on the key type of the generated multimap.
* @since 16.0
*/
public abstract static class MultimapBuilderWithKeys {
private static final int DEFAULT_EXPECTED_VALUES_PER_KEY = 2;
MultimapBuilderWithKeys() {}
abstract Map> createMap();
/** Uses an {@link ArrayList} to store value collections. */
public ListMultimapBuilder arrayListValues() {
return arrayListValues(DEFAULT_EXPECTED_VALUES_PER_KEY);
}
/**
* Uses an {@link ArrayList} to store value collections, initialized to expect the specified
* number of values per key.
*
* @throws IllegalArgumentException if {@code expectedValuesPerKey < 0}
*/
public ListMultimapBuilder arrayListValues(int expectedValuesPerKey) {
checkNonnegative(expectedValuesPerKey, "expectedValuesPerKey");
return new ListMultimapBuilder() {
@Override
public ListMultimap build() {
return Multimaps.newListMultimap(
MultimapBuilderWithKeys.this.createMap(),
new ArrayListSupplier(expectedValuesPerKey));
}
};
}
/** Uses a {@link LinkedList} to store value collections. */
public ListMultimapBuilder linkedListValues() {
return new ListMultimapBuilder() {
@Override
public ListMultimap build() {
return Multimaps.newListMultimap(
MultimapBuilderWithKeys.this.createMap(), LinkedListSupplier.instance());
}
};
}
/** Uses a hash-based {@code Set} to store value collections. */
public SetMultimapBuilder hashSetValues() {
return hashSetValues(DEFAULT_EXPECTED_VALUES_PER_KEY);
}
/**
* Uses a hash-based {@code Set} to store value collections, initialized to expect the specified
* number of values per key.
*
* @throws IllegalArgumentException if {@code expectedValuesPerKey < 0}
*/
public SetMultimapBuilder hashSetValues(int expectedValuesPerKey) {
checkNonnegative(expectedValuesPerKey, "expectedValuesPerKey");
return new SetMultimapBuilder() {
@Override
public SetMultimap build() {
return Multimaps.newSetMultimap(
MultimapBuilderWithKeys.this.createMap(),
new HashSetSupplier(expectedValuesPerKey));
}
};
}
/** Uses an insertion-ordered hash-based {@code Set} to store value collections. */
public SetMultimapBuilder linkedHashSetValues() {
return linkedHashSetValues(DEFAULT_EXPECTED_VALUES_PER_KEY);
}
/**
* Uses an insertion-ordered hash-based {@code Set} to store value collections, initialized to
* expect the specified number of values per key.
*
* @throws IllegalArgumentException if {@code expectedValuesPerKey < 0}
*/
public SetMultimapBuilder linkedHashSetValues(int expectedValuesPerKey) {
checkNonnegative(expectedValuesPerKey, "expectedValuesPerKey");
return new SetMultimapBuilder() {
@Override
public SetMultimap build() {
return Multimaps.newSetMultimap(
MultimapBuilderWithKeys.this.createMap(),
new LinkedHashSetSupplier(expectedValuesPerKey));
}
};
}
/** Uses a naturally-ordered {@link TreeSet} to store value collections. */
@SuppressWarnings("rawtypes")
public SortedSetMultimapBuilder treeSetValues() {
return treeSetValues(Ordering.natural());
}
/**
* Uses a {@link TreeSet} ordered by the specified comparator to store value collections.
*
* Multimaps generated by the resulting builder will not be serializable if {@code
* comparator} is not serializable.
*/
public SortedSetMultimapBuilder treeSetValues(
Comparator comparator) {
checkNotNull(comparator, "comparator");
return new SortedSetMultimapBuilder() {
@Override
public SortedSetMultimap build() {
return Multimaps.newSortedSetMultimap(
MultimapBuilderWithKeys.this.createMap(), new TreeSetSupplier(comparator));
}
};
}
/** Uses an {@link EnumSet} to store value collections. */
public > SetMultimapBuilder enumSetValues(Class valueClass) {
checkNotNull(valueClass, "valueClass");
return new SetMultimapBuilder() {
@Override
public SetMultimap build() {
// V must actually be V0, since enums are effectively final
// (their subclasses are inaccessible)
@SuppressWarnings({"unchecked", "rawtypes"})
Supplier> factory = (Supplier) new EnumSetSupplier(valueClass);
return Multimaps.newSetMultimap(MultimapBuilderWithKeys.this.createMap(), factory);
}
};
}
}
/** Returns a new, empty {@code Multimap} with the specified implementation. */
public abstract Multimap build();
/**
* Returns a {@code Multimap} with the specified implementation, initialized with the entries of
* {@code multimap}.
*/
public Multimap build(
Multimap multimap) {
Multimap result = build();
result.putAll(multimap);
return result;
}
/**
* A specialization of {@link MultimapBuilder} that generates {@link ListMultimap} instances.
*
* @since 16.0
*/
public abstract static class ListMultimapBuilder<
K0 extends @Nullable Object, V0 extends @Nullable Object>
extends MultimapBuilder {
ListMultimapBuilder() {}
@Override
public abstract ListMultimap build();
@Override
public ListMultimap build(
Multimap multimap) {
return (ListMultimap) super.build(multimap);
}
}
/**
* A specialization of {@link MultimapBuilder} that generates {@link SetMultimap} instances.
*
* @since 16.0
*/
public abstract static class SetMultimapBuilder<
K0 extends @Nullable Object, V0 extends @Nullable Object>
extends MultimapBuilder {
SetMultimapBuilder() {}
@Override
public abstract SetMultimap build();
@Override
public SetMultimap build(
Multimap multimap) {
return (SetMultimap) super.build(multimap);
}
}
/**
* A specialization of {@link MultimapBuilder} that generates {@link SortedSetMultimap} instances.
*
* @since 16.0
*/
public abstract static class SortedSetMultimapBuilder<
K0 extends @Nullable Object, V0 extends @Nullable Object>
extends SetMultimapBuilder {
SortedSetMultimapBuilder() {}
@Override
public abstract SortedSetMultimap build();
@Override
public SortedSetMultimap build(
Multimap multimap) {
return (SortedSetMultimap) super.build(multimap);
}
}
}