com.google.common.collect.ImmutableMultimap Maven / Gradle / Ivy
/*
* Copyright (C) 2008 Google Inc.
*
* 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 com.google.common.annotations.GwtCompatible;
import static com.google.common.base.Preconditions.checkNotNull;
import java.io.Serializable;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import javax.annotation.Nullable;
/**
* An immutable {@link Multimap}. Does not permit null keys or values.
*
* Unlike {@link Multimaps#unmodifiableMultimap(Multimap)}, which is
* a view of a separate multimap which can still change, an instance of
* {@code ImmutableMultimap} contains its own data and will never
* change. {@code ImmutableMultimap} is convenient for
* {@code public static final} multimaps ("constant multimaps") and also lets
* you easily make a "defensive copy" of a multimap provided to your class by
* a caller.
*
*
Note: Although this class is not final, it cannot be subclassed as
* it has no public or protected constructors. Thus, instances of this class
* are guaranteed to be immutable.
*
* @author Jared Levy
*/
@GwtCompatible
public abstract class ImmutableMultimap
implements Multimap, Serializable {
/** Returns an empty multimap. */
public static ImmutableMultimap of() {
return ImmutableListMultimap.of();
}
/**
* Returns an immutable multimap containing a single entry.
*/
public static ImmutableMultimap of(K k1, V v1) {
return ImmutableListMultimap.of(k1, v1);
}
/**
* Returns an immutable multimap containing the given entries, in order.
*/
public static ImmutableMultimap of(K k1, V v1, K k2, V v2) {
return ImmutableListMultimap.of(k1, v1, k2, v2);
}
/**
* Returns an immutable multimap containing the given entries, in order.
*/
public static ImmutableMultimap of(
K k1, V v1, K k2, V v2, K k3, V v3) {
return ImmutableListMultimap.of(k1, v1, k2, v2, k3, v3);
}
/**
* Returns an immutable multimap containing the given entries, in order.
*/
public static ImmutableMultimap of(
K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) {
return ImmutableListMultimap.of(k1, v1, k2, v2, k3, v3, k4, v4);
}
/**
* Returns an immutable multimap containing the given entries, in order.
*/
public static ImmutableMultimap of(
K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5) {
return ImmutableListMultimap.of(k1, v1, k2, v2, k3, v3, k4, v4, k5, v5);
}
// looking for of() with > 5 entries? Use the builder instead.
/**
* Returns a new builder. The generated builder is equivalent to the builder
* created by the {@link Builder} constructor.
*/
public static Builder builder() {
return new Builder();
}
/**
* Multimap for {@link ImmutableMultimap.Builder} that maintains key and
* value orderings, allows duplicate values, and performs better than
* {@link LinkedListMultimap}.
*/
private static class BuilderMultimap extends StandardMultimap {
BuilderMultimap() {
super(new LinkedHashMap>());
}
@Override Collection createCollection() {
return Lists.newArrayList();
}
private static final long serialVersionUID = 0;
}
/**
* A builder for creating immutable multimap instances, especially
* {@code public static final} multimaps ("constant multimaps"). Example:
* {@code
*
* static final Multimap STRING_TO_INTEGER_MULTIMAP =
* new ImmutableMultimap.Builder()
* .put("one", 1)
* .putAll("several", 1, 2, 3)
* .putAll("many", 1, 2, 3, 4, 5)
* .build();}
*
* Builder instances can be reused - it is safe to call {@link #build}
* multiple times to build multiple multimaps in series. Each multimap
* contains the key-value mappings in the previously created multimaps.
*/
public static class Builder {
private final Multimap builderMultimap = new BuilderMultimap();
/**
* Creates a new builder. The returned builder is equivalent to the builder
* generated by {@link ImmutableMultimap#builder}.
*/
public Builder() {}
/**
* Adds a key-value mapping to the built multimap.
*/
public Builder put(K key, V value) {
builderMultimap.put(checkNotNull(key), checkNotNull(value));
return this;
}
/**
* Stores a collection of values with the same key in the built multimap.
*
* @throws NullPointerException if {@code key}, {@code values}, or any
* element in {@code values} is null. The builder is left in an invalid
* state.
*/
public Builder putAll(K key, Iterable values) {
Collection valueList = builderMultimap.get(checkNotNull(key));
for (V value : values) {
valueList.add(checkNotNull(value));
}
return this;
}
/**
* Stores an array of values with the same key in the built multimap.
*
* @throws NullPointerException if the key or any value is null. The builder
* is left in an invalid state.
*/
public Builder putAll(K key, V... values) {
return putAll(key, Arrays.asList(values));
}
/**
* Stores another multimap's entries in the built multimap. The generated
* multimap's key and value orderings correspond to the iteration ordering
* of the {@code multimap.asMap()} view, with new keys and values following
* any existing keys and values.
*
* @throws NullPointerException if any key or value in {@code multimap} is
* null. The builder is left in an invalid state.
*/
public Builder putAll(Multimap multimap) {
for (Map.Entry> entry
: multimap.asMap().entrySet()) {
putAll(entry.getKey(), entry.getValue());
}
return this;
}
/**
* Returns a newly-created immutable multimap.
*/
public ImmutableMultimap build() {
return copyOf(builderMultimap);
}
}
/**
* Returns an immutable multimap containing the same mappings as
* {@code multimap}. The generated multimap's key and value orderings
* correspond to the iteration ordering of the {@code multimap.asMap()} view.
*
* Note: Despite what the method name suggests, if
* {@code multimap} is an {@code ImmutableMultimap}, no copy will actually be
* performed, and the given multimap itself will be returned.
*
* @throws NullPointerException if any key or value in {@code multimap} is
* null
*/
public static ImmutableMultimap copyOf(
Multimap multimap) {
if (multimap instanceof ImmutableMultimap) {
@SuppressWarnings("unchecked") // safe since multimap is not writable
ImmutableMultimap kvMultimap
= (ImmutableMultimap) multimap;
return kvMultimap;
} else {
return ImmutableListMultimap.copyOf(multimap);
}
}
final transient ImmutableMap> map;
final transient int size;
// These constants allow the deserialization code to set final fields. This
// holder class makes sure they are not initialized unless an instance is
// deserialized.
static class FieldSettersHolder {
// Eclipse doesn't like the raw ImmutableMultimap
@SuppressWarnings("unchecked")
static final Serialization.FieldSetter
MAP_FIELD_SETTER = Serialization.getFieldSetter(
ImmutableMultimap.class, "map");
// Eclipse doesn't like the raw ImmutableMultimap
@SuppressWarnings("unchecked")
static final Serialization.FieldSetter
SIZE_FIELD_SETTER = Serialization.getFieldSetter(
ImmutableMultimap.class, "size");
}
ImmutableMultimap(ImmutableMap> map,
int size) {
this.map = map;
this.size = size;
}
// mutators (not supported)
/**
* Guaranteed to throw an exception and leave the multimap unmodified.
*
* @throws UnsupportedOperationException always
*/
public ImmutableCollection removeAll(Object key) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the multimap unmodified.
*
* @throws UnsupportedOperationException always
*/
public ImmutableCollection replaceValues(K key,
Iterable values) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the multimap unmodified.
*
* @throws UnsupportedOperationException always
*/
public void clear() {
throw new UnsupportedOperationException();
}
/**
* Returns an immutable collection of the values for the given key. If no
* mappings in the multimap have the provided key, an empty immutable
* collection is returned. The values are in the same order as the parameters
* used to build this multimap.
*/
public abstract ImmutableCollection get(K key);
/**
* Guaranteed to throw an exception and leave the multimap unmodified.
*
* @throws UnsupportedOperationException always
*/
public boolean put(K key, V value) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the multimap unmodified.
*
* @throws UnsupportedOperationException always
*/
public boolean putAll(K key, Iterable values) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the multimap unmodified.
*
* @throws UnsupportedOperationException always
*/
public boolean putAll(Multimap multimap) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the multimap unmodified.
*
* @throws UnsupportedOperationException always
*/
public boolean remove(Object key, Object value) {
throw new UnsupportedOperationException();
}
// accessors
public boolean containsEntry(@Nullable Object key, @Nullable Object value) {
Collection values = map.get(key);
return values != null && values.contains(value);
}
public boolean containsKey(@Nullable Object key) {
return map.containsKey(key);
}
public boolean containsValue(@Nullable Object value) {
for (Collection valueCollection : map.values()) {
if (valueCollection.contains(value)) {
return true;
}
}
return false;
}
public boolean isEmpty() {
return size == 0;
}
public int size() {
return size;
}
@Override public boolean equals(@Nullable Object object) {
if (object instanceof Multimap) {
Multimap that = (Multimap) object;
return this.map.equals(that.asMap());
}
return false;
}
@Override public int hashCode() {
return map.hashCode();
}
@Override public String toString() {
return map.toString();
}
// views
/**
* Returns an immutable set of the distinct keys in this multimap. These keys
* are ordered according to when they first appeared during the construction
* of this multimap.
*/
public ImmutableSet keySet() {
return map.keySet();
}
/**
* Returns an immutable map that associates each key with its corresponding
* values in the multimap.
*/
@SuppressWarnings("unchecked") // a widening cast
public ImmutableMap> asMap() {
return (ImmutableMap) map;
}
private transient ImmutableCollection> entries;
/**
* Returns an immutable collection of all key-value pairs in the multimap. Its
* iterator traverses the values for the first key, the values for the second
* key, and so on.
*/
public ImmutableCollection> entries() {
ImmutableCollection> result = entries;
return (result == null)
? (entries = new EntryCollection(this)) : result;
}
private static class EntryCollection
extends ImmutableCollection> {
final ImmutableMultimap multimap;
EntryCollection(ImmutableMultimap multimap) {
this.multimap = multimap;
}
@Override public UnmodifiableIterator> iterator() {
final Iterator>>
mapIterator = this.multimap.map.entrySet().iterator();
return new UnmodifiableIterator>() {
K key;
Iterator valueIterator;
public boolean hasNext() {
return (key != null && valueIterator.hasNext())
|| mapIterator.hasNext();
}
public Map.Entry next() {
if (key == null || !valueIterator.hasNext()) {
Map.Entry> entry
= mapIterator.next();
key = entry.getKey();
valueIterator = entry.getValue().iterator();
}
return Maps.immutableEntry(key, valueIterator.next());
}
};
}
public int size() {
return multimap.size();
}
@Override public boolean contains(Object object) {
if (object instanceof Map.Entry) {
Map.Entry entry = (Map.Entry) object;
return multimap.containsEntry(entry.getKey(), entry.getValue());
}
return false;
}
private static final long serialVersionUID = 0;
}
private transient ImmutableMultiset keys;
/**
* Returns a collection, which may contain duplicates, of all keys. The number
* of times a key appears in the returned multiset equals the number of
* mappings the key has in the multimap. Duplicate keys appear consecutively
* in the multiset's iteration order.
*/
public ImmutableMultiset keys() {
ImmutableMultiset result = keys;
return (result == null)
? (keys = new ImmutableMultiset(createCountMap(), size))
: result;
}
/**
* TODO: Instead of calling createCountMap(), which creates a copy, it would
* better to create an ImmutableMultiset through its public methods. That will
* be easier once we have an ImmutableMultiset builder.
*/
private ImmutableMap createCountMap() {
ImmutableMap.Builder builder = ImmutableMap.builder();
for (Map.Entry entry : map.entrySet()) {
builder.put(entry.getKey(), entry.getValue().size());
}
return builder.build();
}
private transient ImmutableCollection values;
/**
* Returns an immutable collection of the values in this multimap. Its
* iterator traverses the values for the first key, the values for the second
* key, and so on.
*/
public ImmutableCollection values() {
ImmutableCollection result = values;
return (result == null) ? (values = new Values(this)) : result;
}
private static class Values extends ImmutableCollection {
final Multimap multimap;
Values(Multimap multimap) {
this.multimap = multimap;
}
@Override public UnmodifiableIterator iterator() {
final Iterator> entryIterator
= multimap.entries().iterator();
return new UnmodifiableIterator() {
public boolean hasNext() {
return entryIterator.hasNext();
}
public V next() {
return entryIterator.next().getValue();
}
};
}
public int size() {
return multimap.size();
}
private static final long serialVersionUID = 0;
}
private static final long serialVersionUID = 0;
}