ImmutableMultimap.java
/*
* 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.checkNotNull;
import static com.google.common.collect.CollectPreconditions.checkEntryNotNull;
import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.DoNotMock;
import com.google.j2objc.annotations.Weak;
import com.google.j2objc.annotations.WeakOuter;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Comparator;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.Spliterator;
import java.util.function.BiConsumer;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* A {@link Multimap} whose contents will never change, with many other important properties
* detailed at {@link ImmutableCollection}.
*
* <p><b>Warning:</b> avoid <i>direct</i> usage of {@link ImmutableMultimap} as a type (as with
* {@link Multimap} itself). Prefer subtypes such as {@link ImmutableSetMultimap} or {@link
* ImmutableListMultimap}, which have well-defined {@link #equals} semantics, thus avoiding a common
* source of bugs and confusion.
*
* <p><b>Note:</b> every {@link ImmutableMultimap} offers an {@link #inverse} view, so there is no
* need for a distinct {@code ImmutableBiMultimap} type.
*
* <p><a id="iteration"></a>
*
* <p><b>Key-grouped iteration.</b> All view collections follow the same iteration order. In all
* current implementations, the iteration order always keeps multiple entries with the same key
* together. Any creation method that would customarily respect insertion order (such as {@link
* #copyOf(Multimap)}) instead preserves key-grouped order by inserting entries for an existing key
* immediately after the last entry having that key.
*
* <p>See the Guava User Guide article on <a href=
* "https://github.com/google/guava/wiki/ImmutableCollectionsExplained"> immutable collections</a>.
*
* @author Jared Levy
* @since 2.0
*/
@GwtCompatible(emulated = true)
public abstract class ImmutableMultimap<K, V> extends BaseImmutableMultimap<K, V>
implements Serializable {
/**
* Returns an empty multimap.
*
* <p><b>Performance note:</b> the instance returned is a singleton.
*/
public static <K, V> ImmutableMultimap<K, V> of() {
return ImmutableListMultimap.of();
}
/** Returns an immutable multimap containing a single entry. */
public static <K, V> ImmutableMultimap<K, V> of(K k1, V v1) {
return ImmutableListMultimap.of(k1, v1);
}
/** Returns an immutable multimap containing the given entries, in order. */
public static <K, V> ImmutableMultimap<K, V> 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 the "key-grouped" insertion
* order described in the <a href="#iteration">class documentation</a>.
*/
public static <K, V> ImmutableMultimap<K, V> 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 the "key-grouped" insertion
* order described in the <a href="#iteration">class documentation</a>.
*/
public static <K, V> ImmutableMultimap<K, V> 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 the "key-grouped" insertion
* order described in the <a href="#iteration">class documentation</a>.
*/
public static <K, V> ImmutableMultimap<K, V> 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 <K, V> Builder<K, V> builder() {
return new Builder<>();
}
/**
* A builder for creating immutable multimap instances, especially {@code public static final}
* multimaps ("constant multimaps"). Example:
*
* <pre>{@code
* static final Multimap<String, Integer> STRING_TO_INTEGER_MULTIMAP =
* new ImmutableMultimap.Builder<String, Integer>()
* .put("one", 1)
* .putAll("several", 1, 2, 3)
* .putAll("many", 1, 2, 3, 4, 5)
* .build();
* }</pre>
*
* <p>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.
*
* @since 2.0
*/
@DoNotMock
public static class Builder<K, V> {
Map<K, Collection<V>> builderMap;
@Nullable Comparator<? super K> keyComparator;
@Nullable Comparator<? super V> valueComparator;
/**
* Creates a new builder. The returned builder is equivalent to the builder generated by {@link
* ImmutableMultimap#builder}.
*/
public Builder() {
this.builderMap = Platform.preservesInsertionOrderOnPutsMap();
}
Collection<V> newMutableValueCollection() {
return new ArrayList<>();
}
/** Adds a key-value mapping to the built multimap. */
@CanIgnoreReturnValue
public Builder<K, V> put(K key, V value) {
checkEntryNotNull(key, value);
Collection<V> valueCollection = builderMap.get(key);
if (valueCollection == null) {
builderMap.put(key, valueCollection = newMutableValueCollection());
}
valueCollection.add(value);
return this;
}
/**
* Adds an entry to the built multimap.
*
* @since 11.0
*/
@CanIgnoreReturnValue
public Builder<K, V> put(Entry<? extends K, ? extends V> entry) {
return put(entry.getKey(), entry.getValue());
}
/**
* Adds entries to the built multimap.
*
* @since 19.0
*/
@CanIgnoreReturnValue
@Beta
public Builder<K, V> putAll(Iterable<? extends Entry<? extends K, ? extends V>> entries) {
for (Entry<? extends K, ? extends V> entry : entries) {
put(entry);
}
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.
*/
@CanIgnoreReturnValue
public Builder<K, V> putAll(K key, Iterable<? extends V> values) {
if (key == null) {
throw new NullPointerException("null key in entry: null=" + Iterables.toString(values));
}
Collection<V> valueCollection = builderMap.get(key);
if (valueCollection != null) {
for (V value : values) {
checkEntryNotNull(key, value);
valueCollection.add(value);
}
return this;
}
Iterator<? extends V> valuesItr = values.iterator();
if (!valuesItr.hasNext()) {
return this;
}
valueCollection = newMutableValueCollection();
while (valuesItr.hasNext()) {
V value = valuesItr.next();
checkEntryNotNull(key, value);
valueCollection.add(value);
}
builderMap.put(key, valueCollection);
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.
*/
@CanIgnoreReturnValue
public Builder<K, V> 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.
*/
@CanIgnoreReturnValue
public Builder<K, V> putAll(Multimap<? extends K, ? extends V> multimap) {
for (Entry<? extends K, ? extends Collection<? extends V>> entry :
multimap.asMap().entrySet()) {
putAll(entry.getKey(), entry.getValue());
}
return this;
}
/**
* Specifies the ordering of the generated multimap's keys.
*
* @since 8.0
*/
@CanIgnoreReturnValue
public Builder<K, V> orderKeysBy(Comparator<? super K> keyComparator) {
this.keyComparator = checkNotNull(keyComparator);
return this;
}
/**
* Specifies the ordering of the generated multimap's values for each key.
*
* @since 8.0
*/
@CanIgnoreReturnValue
public Builder<K, V> orderValuesBy(Comparator<? super V> valueComparator) {
this.valueComparator = checkNotNull(valueComparator);
return this;
}
@CanIgnoreReturnValue
Builder<K, V> combine(Builder<K, V> other) {
for (Map.Entry<K, Collection<V>> entry : other.builderMap.entrySet()) {
putAll(entry.getKey(), entry.getValue());
}
return this;
}
/** Returns a newly-created immutable multimap. */
public ImmutableMultimap<K, V> build() {
Collection<Map.Entry<K, Collection<V>>> mapEntries = builderMap.entrySet();
if (keyComparator != null) {
mapEntries = Ordering.from(keyComparator).<K>onKeys().immutableSortedCopy(mapEntries);
}
return ImmutableListMultimap.fromMapEntries(mapEntries, valueComparator);
}
}
/**
* Returns an immutable multimap containing the same mappings as {@code multimap}, in the
* "key-grouped" iteration order described in the class documentation.
*
* <p>Despite the method name, this method attempts to avoid actually copying the data when it is
* safe to do so. The exact circumstances under which a copy will or will not be performed are
* undocumented and subject to change.
*
* @throws NullPointerException if any key or value in {@code multimap} is null
*/
public static <K, V> ImmutableMultimap<K, V> copyOf(Multimap<? extends K, ? extends V> multimap) {
if (multimap instanceof ImmutableMultimap) {
@SuppressWarnings("unchecked") // safe since multimap is not writable
ImmutableMultimap<K, V> kvMultimap = (ImmutableMultimap<K, V>) multimap;
if (!kvMultimap.isPartialView()) {
return kvMultimap;
}
}
return ImmutableListMultimap.copyOf(multimap);
}
/**
* Returns an immutable multimap containing the specified entries. The returned multimap iterates
* over keys in the order they were first encountered in the input, and the values for each key
* are iterated in the order they were encountered.
*
* @throws NullPointerException if any key, value, or entry is null
* @since 19.0
*/
@Beta
public static <K, V> ImmutableMultimap<K, V> copyOf(
Iterable<? extends Entry<? extends K, ? extends V>> entries) {
return ImmutableListMultimap.copyOf(entries);
}
final transient ImmutableMap<K, ? extends ImmutableCollection<V>> 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.
@GwtIncompatible // java serialization is not supported
static class FieldSettersHolder {
static final Serialization.FieldSetter<ImmutableMultimap> MAP_FIELD_SETTER =
Serialization.getFieldSetter(ImmutableMultimap.class, "map");
static final Serialization.FieldSetter<ImmutableMultimap> SIZE_FIELD_SETTER =
Serialization.getFieldSetter(ImmutableMultimap.class, "size");
}
ImmutableMultimap(ImmutableMap<K, ? extends ImmutableCollection<V>> 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
* @deprecated Unsupported operation.
*/
@CanIgnoreReturnValue
@Deprecated
@Override
public ImmutableCollection<V> removeAll(Object key) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the multimap unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@CanIgnoreReturnValue
@Deprecated
@Override
public ImmutableCollection<V> replaceValues(K key, Iterable<? extends V> values) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the multimap unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated
@Override
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.
*/
@Override
public abstract ImmutableCollection<V> get(K key);
/**
* Returns an immutable multimap which is the inverse of this one. For every key-value mapping in
* the original, the result will have a mapping with key and value reversed.
*
* @since 11.0
*/
public abstract ImmutableMultimap<V, K> inverse();
/**
* Guaranteed to throw an exception and leave the multimap unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@CanIgnoreReturnValue
@Deprecated
@Override
public boolean put(K key, V value) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the multimap unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@CanIgnoreReturnValue
@Deprecated
@Override
public boolean putAll(K key, Iterable<? extends V> values) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the multimap unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@CanIgnoreReturnValue
@Deprecated
@Override
public boolean putAll(Multimap<? extends K, ? extends V> multimap) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the multimap unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@CanIgnoreReturnValue
@Deprecated
@Override
public boolean remove(Object key, Object value) {
throw new UnsupportedOperationException();
}
/**
* Returns {@code true} if this immutable multimap's implementation contains references to
* user-created objects that aren't accessible via this multimap's methods. This is generally used
* to determine whether {@code copyOf} implementations should make an explicit copy to avoid
* memory leaks.
*/
boolean isPartialView() {
return map.isPartialView();
}
// accessors
@Override
public boolean containsKey(@Nullable Object key) {
return map.containsKey(key);
}
@Override
public boolean containsValue(@Nullable Object value) {
return value != null && super.containsValue(value);
}
@Override
public int size() {
return size;
}
// views
/**
* Returns an immutable set of the distinct keys in this multimap, in the same order as they
* appear in this multimap.
*/
@Override
public ImmutableSet<K> keySet() {
return map.keySet();
}
@Override
Set<K> createKeySet() {
throw new AssertionError("unreachable");
}
/**
* Returns an immutable map that associates each key with its corresponding values in the
* multimap. Keys and values appear in the same order as in this multimap.
*/
@Override
@SuppressWarnings("unchecked") // a widening cast
public ImmutableMap<K, Collection<V>> asMap() {
return (ImmutableMap) map;
}
@Override
Map<K, Collection<V>> createAsMap() {
throw new AssertionError("should never be called");
}
/** Returns an immutable collection of all key-value pairs in the multimap. */
@Override
public ImmutableCollection<Entry<K, V>> entries() {
return (ImmutableCollection<Entry<K, V>>) super.entries();
}
@Override
ImmutableCollection<Entry<K, V>> createEntries() {
return new EntryCollection<>(this);
}
private static class EntryCollection<K, V> extends ImmutableCollection<Entry<K, V>> {
@Weak final ImmutableMultimap<K, V> multimap;
EntryCollection(ImmutableMultimap<K, V> multimap) {
this.multimap = multimap;
}
@Override
public UnmodifiableIterator<Entry<K, V>> iterator() {
return multimap.entryIterator();
}
@Override
boolean isPartialView() {
return multimap.isPartialView();
}
@Override
public int size() {
return multimap.size();
}
@Override
public boolean contains(Object object) {
if (object instanceof Entry) {
Entry<?, ?> entry = (Entry<?, ?>) object;
return multimap.containsEntry(entry.getKey(), entry.getValue());
}
return false;
}
private static final long serialVersionUID = 0;
}
@Override
UnmodifiableIterator<Entry<K, V>> entryIterator() {
return new UnmodifiableIterator<Entry<K, V>>() {
final Iterator<? extends Entry<K, ? extends ImmutableCollection<V>>> asMapItr =
map.entrySet().iterator();
K currentKey = null;
Iterator<V> valueItr = Iterators.emptyIterator();
@Override
public boolean hasNext() {
return valueItr.hasNext() || asMapItr.hasNext();
}
@Override
public Entry<K, V> next() {
if (!valueItr.hasNext()) {
Entry<K, ? extends ImmutableCollection<V>> entry = asMapItr.next();
currentKey = entry.getKey();
valueItr = entry.getValue().iterator();
}
return Maps.immutableEntry(currentKey, valueItr.next());
}
};
}
@Override
Spliterator<Entry<K, V>> entrySpliterator() {
return CollectSpliterators.flatMap(
asMap().entrySet().spliterator(),
keyToValueCollectionEntry -> {
K key = keyToValueCollectionEntry.getKey();
Collection<V> valueCollection = keyToValueCollectionEntry.getValue();
return CollectSpliterators.map(
valueCollection.spliterator(), (V value) -> Maps.immutableEntry(key, value));
},
Spliterator.SIZED | (this instanceof SetMultimap ? Spliterator.DISTINCT : 0),
size());
}
@Override
public void forEach(BiConsumer<? super K, ? super V> action) {
checkNotNull(action);
asMap()
.forEach(
(key, valueCollection) -> valueCollection.forEach(value -> action.accept(key, value)));
}
/**
* Returns an immutable multiset containing all the keys in this multimap, in the same order and
* with the same frequencies as they appear in this multimap; to get only a single occurrence of
* each key, use {@link #keySet}.
*/
@Override
public ImmutableMultiset<K> keys() {
return (ImmutableMultiset<K>) super.keys();
}
@Override
ImmutableMultiset<K> createKeys() {
return new Keys();
}
@SuppressWarnings("serial") // Uses writeReplace, not default serialization
@WeakOuter
class Keys extends ImmutableMultiset<K> {
@Override
public boolean contains(@Nullable Object object) {
return containsKey(object);
}
@Override
public int count(@Nullable Object element) {
Collection<V> values = map.get(element);
return (values == null) ? 0 : values.size();
}
@Override
public ImmutableSet<K> elementSet() {
return keySet();
}
@Override
public int size() {
return ImmutableMultimap.this.size();
}
@Override
Multiset.Entry<K> getEntry(int index) {
Map.Entry<K, ? extends Collection<V>> entry = map.entrySet().asList().get(index);
return Multisets.immutableEntry(entry.getKey(), entry.getValue().size());
}
@Override
boolean isPartialView() {
return true;
}
@GwtIncompatible
@Override
Object writeReplace() {
return new KeysSerializedForm(ImmutableMultimap.this);
}
}
@GwtIncompatible
private static final class KeysSerializedForm implements Serializable {
final ImmutableMultimap<?, ?> multimap;
KeysSerializedForm(ImmutableMultimap<?, ?> multimap) {
this.multimap = multimap;
}
Object readResolve() {
return multimap.keys();
}
}
/**
* 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.
*/
@Override
public ImmutableCollection<V> values() {
return (ImmutableCollection<V>) super.values();
}
@Override
ImmutableCollection<V> createValues() {
return new Values<>(this);
}
@Override
UnmodifiableIterator<V> valueIterator() {
return new UnmodifiableIterator<V>() {
Iterator<? extends ImmutableCollection<V>> valueCollectionItr = map.values().iterator();
Iterator<V> valueItr = Iterators.emptyIterator();
@Override
public boolean hasNext() {
return valueItr.hasNext() || valueCollectionItr.hasNext();
}
@Override
public V next() {
if (!valueItr.hasNext()) {
valueItr = valueCollectionItr.next().iterator();
}
return valueItr.next();
}
};
}
private static final class Values<K, V> extends ImmutableCollection<V> {
@Weak private final transient ImmutableMultimap<K, V> multimap;
Values(ImmutableMultimap<K, V> multimap) {
this.multimap = multimap;
}
@Override
public boolean contains(@Nullable Object object) {
return multimap.containsValue(object);
}
@Override
public UnmodifiableIterator<V> iterator() {
return multimap.valueIterator();
}
@GwtIncompatible // not present in emulated superclass
@Override
int copyIntoArray(Object[] dst, int offset) {
for (ImmutableCollection<V> valueCollection : multimap.map.values()) {
offset = valueCollection.copyIntoArray(dst, offset);
}
return offset;
}
@Override
public int size() {
return multimap.size();
}
@Override
boolean isPartialView() {
return true;
}
private static final long serialVersionUID = 0;
}
private static final long serialVersionUID = 0;
}