/*
* 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.Beta;
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.HashMap;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
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;
/**
* A builder for a multimap implementation that allows customization of the backing map and value
* collection implementations used in a particular multimap.
*
* <p>This can be used to easily configure multimap data structure implementations not provided
* explicitly in {@code com.google.common.collect}, for example:
*
* <pre> {@code
* ListMultimap<String, Integer> treeListMultimap =
* MultimapBuilder.treeKeys().arrayListValues().build();
* SetMultimap<Integer, MyEnum> hashEnumMultimap =
* MultimapBuilder.hashKeys().enumSetValues(MyEnum.class).build();}</pre>
*
* <p>{@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.
*
* <p>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 <K0> An upper bound on the key type of the generated multimap.
* @param <V0> An upper bound on the value type of the generated multimap.
* @since 16.0
*/
@Beta
@GwtCompatible
public abstract class MultimapBuilder<K0, V0> {
/*
* 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 {@link HashMap} to map keys to value collections.
*/
public static MultimapBuilderWithKeys<Object> hashKeys() {
return hashKeys(DEFAULT_EXPECTED_KEYS);
}
/**
* Uses a {@link HashMap} to map keys to value collections, initialized to expect the specified
* number of keys.
*
* @throws IllegalArgumentException if {@code expectedKeys < 0}
*/
public static MultimapBuilderWithKeys<Object> hashKeys(final int expectedKeys) {
checkNonnegative(expectedKeys, "expectedKeys");
return new MultimapBuilderWithKeys<Object>() {
@Override
<K, V> Map<K, Collection<V>> createMap() {
return new HashMap<K, Collection<V>>(expectedKeys);
}
};
}
/**
* Uses a {@link LinkedHashMap} to map keys to value collections.
*
* <p>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<Object> linkedHashKeys() {
return linkedHashKeys(DEFAULT_EXPECTED_KEYS);
}
/**
* Uses a {@link LinkedHashMap} to map keys to value collections, initialized to expect the
* specified number of keys.
*
* <p>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<Object> linkedHashKeys(final int expectedKeys) {
checkNonnegative(expectedKeys, "expectedKeys");
return new MultimapBuilderWithKeys<Object>() {
@Override
<K, V> Map<K, Collection<V>> createMap() {
return new LinkedHashMap<K, Collection<V>>(expectedKeys);
}
};
}
/**
* Uses a naturally-ordered {@link TreeMap} to map keys to value collections.
*
* <p>The collections returned by {@link Multimap#keySet()}, {@link Multimap#keys()}, and
* {@link Multimap#asMap()} will iterate through the keys in sorted order.
*
* <p>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<Comparable> treeKeys() {
return treeKeys(Ordering.natural());
}
/**
* Uses a {@link TreeMap} sorted by the specified comparator to map keys to value collections.
*
* <p>The collections returned by {@link Multimap#keySet()}, {@link Multimap#keys()}, and
* {@link Multimap#asMap()} will iterate through the keys in sorted order.
*
* <p>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}.
*
* <p>Multimaps generated by the resulting builder will not be serializable if {@code comparator}
* is not serializable.
*/
public static <K0> MultimapBuilderWithKeys<K0> treeKeys(final Comparator<K0> comparator) {
checkNotNull(comparator);
return new MultimapBuilderWithKeys<K0>() {
@Override
<K extends K0, V> Map<K, Collection<V>> createMap() {
return new TreeMap<K, Collection<V>>(comparator);
}
};
}
/**
* Uses an {@link EnumMap} to map keys to value collections.
*/
public static <K0 extends Enum<K0>> MultimapBuilderWithKeys<K0> enumKeys(
final Class<K0> keyClass) {
checkNotNull(keyClass);
return new MultimapBuilderWithKeys<K0>() {
@SuppressWarnings("unchecked")
@Override
<K extends K0, V> Map<K, Collection<V>> createMap() {
// K must actually be K0, since enums are effectively final
// (their subclasses are inaccessible)
return (Map<K, Collection<V>>) new EnumMap<K0, Collection<V>>(keyClass);
}
};
}
private static final class ArrayListSupplier<V> implements Supplier<List<V>>, Serializable {
private final int expectedValuesPerKey;
ArrayListSupplier(int expectedValuesPerKey) {
this.expectedValuesPerKey = checkNonnegative(expectedValuesPerKey, "expectedValuesPerKey");
}
@Override
public List<V> get() {
return new ArrayList<V>(expectedValuesPerKey);
}
}
private enum LinkedListSupplier implements Supplier<List<Object>> {
INSTANCE;
public static <V> Supplier<List<V>> instance() {
// Each call generates a fresh LinkedList, which can serve as a List<V> for any V.
@SuppressWarnings({"rawtypes", "unchecked"})
Supplier<List<V>> result = (Supplier) INSTANCE;
return result;
}
@Override
public List<Object> get() {
return new LinkedList<Object>();
}
}
private static final class HashSetSupplier<V> implements Supplier<Set<V>>, Serializable {
private final int expectedValuesPerKey;
HashSetSupplier(int expectedValuesPerKey) {
this.expectedValuesPerKey = checkNonnegative(expectedValuesPerKey, "expectedValuesPerKey");
}
@Override
public Set<V> get() {
return new HashSet<V>(expectedValuesPerKey);
}
}
private static final class LinkedHashSetSupplier<V> implements Supplier<Set<V>>, Serializable {
private final int expectedValuesPerKey;
LinkedHashSetSupplier(int expectedValuesPerKey) {
this.expectedValuesPerKey = checkNonnegative(expectedValuesPerKey, "expectedValuesPerKey");
}
@Override
public Set<V> get() {
return new LinkedHashSet<V>(expectedValuesPerKey);
}
}
private static final class TreeSetSupplier<V> implements Supplier<SortedSet<V>>, Serializable {
private final Comparator<? super V> comparator;
TreeSetSupplier(Comparator<? super V> comparator) {
this.comparator = checkNotNull(comparator);
}
@Override
public SortedSet<V> get() {
return new TreeSet<V>(comparator);
}
}
private static final class EnumSetSupplier<V extends Enum<V>>
implements Supplier<Set<V>>, Serializable {
private final Class<V> clazz;
EnumSetSupplier(Class<V> clazz) {
this.clazz = checkNotNull(clazz);
}
@Override
public Set<V> 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 <K0> The upper bound on the key type of the generated multimap.
*/
public abstract static class MultimapBuilderWithKeys<K0> {
private static final int DEFAULT_EXPECTED_VALUES_PER_KEY = 2;
MultimapBuilderWithKeys() {}
abstract <K extends K0, V> Map<K, Collection<V>> createMap();
/**
* Uses an {@link ArrayList} to store value collections.
*/
public ListMultimapBuilder<K0, Object> 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<K0, Object> arrayListValues(final int expectedValuesPerKey) {
checkNonnegative(expectedValuesPerKey, "expectedValuesPerKey");
return new ListMultimapBuilder<K0, Object>() {
@Override
public <K extends K0, V> ListMultimap<K, V> build() {
return Multimaps.newListMultimap(
MultimapBuilderWithKeys.this.<K, V>createMap(),
new ArrayListSupplier<V>(expectedValuesPerKey));
}
};
}
/**
* Uses a {@link LinkedList} to store value collections.
*/
public ListMultimapBuilder<K0, Object> linkedListValues() {
return new ListMultimapBuilder<K0, Object>() {
@Override
public <K extends K0, V> ListMultimap<K, V> build() {
return Multimaps.newListMultimap(
MultimapBuilderWithKeys.this.<K, V>createMap(),
LinkedListSupplier.<V>instance());
}
};
}
/**
* Uses a {@link HashSet} to store value collections.
*/
public SetMultimapBuilder<K0, Object> hashSetValues() {
return hashSetValues(DEFAULT_EXPECTED_VALUES_PER_KEY);
}
/**
* Uses a {@link HashSet} to store value collections, initialized to expect the specified number
* of values per key.
*
* @throws IllegalArgumentException if {@code expectedValuesPerKey < 0}
*/
public SetMultimapBuilder<K0, Object> hashSetValues(final int expectedValuesPerKey) {
checkNonnegative(expectedValuesPerKey, "expectedValuesPerKey");
return new SetMultimapBuilder<K0, Object>() {
@Override
public <K extends K0, V> SetMultimap<K, V> build() {
return Multimaps.newSetMultimap(
MultimapBuilderWithKeys.this.<K, V>createMap(),
new HashSetSupplier<V>(expectedValuesPerKey));
}
};
}
/**
* Uses a {@link LinkedHashSet} to store value collections.
*/
public SetMultimapBuilder<K0, Object> linkedHashSetValues() {
return linkedHashSetValues(DEFAULT_EXPECTED_VALUES_PER_KEY);
}
/**
* Uses a {@link LinkedHashSet} to store value collections, initialized to expect the specified
* number of values per key.
*
* @throws IllegalArgumentException if {@code expectedValuesPerKey < 0}
*/
public SetMultimapBuilder<K0, Object> linkedHashSetValues(final int expectedValuesPerKey) {
checkNonnegative(expectedValuesPerKey, "expectedValuesPerKey");
return new SetMultimapBuilder<K0, Object>() {
@Override
public <K extends K0, V> SetMultimap<K, V> build() {
return Multimaps.newSetMultimap(
MultimapBuilderWithKeys.this.<K, V>createMap(),
new LinkedHashSetSupplier<V>(expectedValuesPerKey));
}
};
}
/**
* Uses a naturally-ordered {@link TreeSet} to store value collections.
*/
@SuppressWarnings("rawtypes")
public SortedSetMultimapBuilder<K0, Comparable> treeSetValues() {
return treeSetValues(Ordering.natural());
}
/**
* Uses a {@link TreeSet} ordered by the specified comparator to store value collections.
*
* <p>Multimaps generated by the resulting builder will not be serializable if
* {@code comparator} is not serializable.
*/
public <V0> SortedSetMultimapBuilder<K0, V0> treeSetValues(final Comparator<V0> comparator) {
checkNotNull(comparator, "comparator");
return new SortedSetMultimapBuilder<K0, V0>() {
@Override
public <K extends K0, V extends V0> SortedSetMultimap<K, V> build() {
return Multimaps.newSortedSetMultimap(
MultimapBuilderWithKeys.this.<K, V>createMap(),
new TreeSetSupplier<V>(comparator));
}
};
}
/**
* Uses an {@link EnumSet} to store value collections.
*/
public <V0 extends Enum<V0>> SetMultimapBuilder<K0, V0> enumSetValues(
final Class<V0> valueClass) {
checkNotNull(valueClass, "valueClass");
return new SetMultimapBuilder<K0, V0>() {
@Override
public <K extends K0, V extends V0> SetMultimap<K, V> build() {
// V must actually be V0, since enums are effectively final
// (their subclasses are inaccessible)
@SuppressWarnings({"unchecked", "rawtypes"})
Supplier<Set<V>> factory = (Supplier) new EnumSetSupplier<V0>(valueClass);
return Multimaps.newSetMultimap(
MultimapBuilderWithKeys.this.<K, V>createMap(),
factory);
}
};
}
}
/**
* Returns a new, empty {@code Multimap} with the specified implementation.
*/
public abstract <K extends K0, V extends V0> Multimap<K, V> build();
/**
* Returns a {@code Multimap} with the specified implementation, initialized with the entries of
* {@code multimap}.
*/
public <K extends K0, V extends V0> Multimap<K, V> build(
Multimap<? extends K, ? extends V> multimap) {
Multimap<K, V> result = build();
result.putAll(multimap);
return result;
}
/**
* A specialization of {@link MultimapBuilder} that generates {@link ListMultimap} instances.
*/
public abstract static class ListMultimapBuilder<K0, V0> extends MultimapBuilder<K0, V0> {
ListMultimapBuilder() {}
@Override
public abstract <K extends K0, V extends V0> ListMultimap<K, V> build();
@Override
public <K extends K0, V extends V0> ListMultimap<K, V> build(
Multimap<? extends K, ? extends V> multimap) {
return (ListMultimap<K, V>) super.build(multimap);
}
}
/**
* A specialization of {@link MultimapBuilder} that generates {@link SetMultimap} instances.
*/
public abstract static class SetMultimapBuilder<K0, V0> extends MultimapBuilder<K0, V0> {
SetMultimapBuilder() {}
@Override
public abstract <K extends K0, V extends V0> SetMultimap<K, V> build();
@Override
public <K extends K0, V extends V0> SetMultimap<K, V> build(
Multimap<? extends K, ? extends V> multimap) {
return (SetMultimap<K, V>) super.build(multimap);
}
}
/**
* A specialization of {@link MultimapBuilder} that generates {@link SortedSetMultimap} instances.
*/
public abstract static class SortedSetMultimapBuilder<K0, V0> extends SetMultimapBuilder<K0, V0> {
SortedSetMultimapBuilder() {}
@Override
public abstract <K extends K0, V extends V0> SortedSetMultimap<K, V> build();
@Override
public <K extends K0, V extends V0> SortedSetMultimap<K, V> build(
Multimap<? extends K, ? extends V> multimap) {
return (SortedSetMultimap<K, V>) super.build(multimap);
}
}
}