ImmutableSetMultimap.java
/*
* Copyright (C) 2009 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 com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.base.MoreObjects;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.DoNotCall;
import com.google.errorprone.annotations.concurrent.LazyInit;
import com.google.j2objc.annotations.RetainedWith;
import com.google.j2objc.annotations.Weak;
import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Arrays;
import java.util.Collection;
import java.util.Comparator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.function.Function;
import java.util.stream.Collector;
import java.util.stream.Stream;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* A {@link SetMultimap} whose contents will never change, with many other important properties
* detailed at {@link ImmutableCollection}.
*
* <p><b>Warning:</b> As in all {@link SetMultimap}s, do not modify either a key <i>or a value</i>
* of a {@code ImmutableSetMultimap} in a way that affects its {@link Object#equals} behavior.
* Undefined behavior and bugs will result.
*
* <p>See the Guava User Guide article on <a href=
* "https://github.com/google/guava/wiki/ImmutableCollectionsExplained"> immutable collections</a>.
*
* @author Mike Ward
* @since 2.0
*/
@GwtCompatible(serializable = true, emulated = true)
public class ImmutableSetMultimap<K, V> extends ImmutableMultimap<K, V>
implements SetMultimap<K, V> {
/**
* Returns a {@link Collector} that accumulates elements into an {@code ImmutableSetMultimap}
* whose keys and values are the result of applying the provided mapping functions to the input
* elements.
*
* <p>For streams with defined encounter order (as defined in the Ordering section of the {@link
* java.util.stream} Javadoc), that order is preserved, but entries are <a
* href="ImmutableMultimap.html#iteration">grouped by key</a>.
*
* <p>Example:
*
* <pre>{@code
* static final Multimap<Character, String> FIRST_LETTER_MULTIMAP =
* Stream.of("banana", "apple", "carrot", "asparagus", "cherry")
* .collect(toImmutableSetMultimap(str -> str.charAt(0), str -> str.substring(1)));
*
* // is equivalent to
*
* static final Multimap<Character, String> FIRST_LETTER_MULTIMAP =
* new ImmutableSetMultimap.Builder<Character, String>()
* .put('b', "anana")
* .putAll('a', "pple", "sparagus")
* .putAll('c', "arrot", "herry")
* .build();
* }</pre>
*
* @since 21.0
*/
public static <T, K, V> Collector<T, ?, ImmutableSetMultimap<K, V>> toImmutableSetMultimap(
Function<? super T, ? extends K> keyFunction,
Function<? super T, ? extends V> valueFunction) {
return CollectCollectors.toImmutableSetMultimap(keyFunction, valueFunction);
}
/**
* Returns a {@code Collector} accumulating entries into an {@code ImmutableSetMultimap}. Each
* input element is mapped to a key and a stream of values, each of which are put into the
* resulting {@code Multimap}, in the encounter order of the stream and the encounter order of the
* streams of values.
*
* <p>Example:
*
* <pre>{@code
* static final ImmutableSetMultimap<Character, Character> FIRST_LETTER_MULTIMAP =
* Stream.of("banana", "apple", "carrot", "asparagus", "cherry")
* .collect(
* flatteningToImmutableSetMultimap(
* str -> str.charAt(0),
* str -> str.substring(1).chars().mapToObj(c -> (char) c));
*
* // is equivalent to
*
* static final ImmutableSetMultimap<Character, Character> FIRST_LETTER_MULTIMAP =
* ImmutableSetMultimap.<Character, Character>builder()
* .putAll('b', Arrays.asList('a', 'n', 'a', 'n', 'a'))
* .putAll('a', Arrays.asList('p', 'p', 'l', 'e'))
* .putAll('c', Arrays.asList('a', 'r', 'r', 'o', 't'))
* .putAll('a', Arrays.asList('s', 'p', 'a', 'r', 'a', 'g', 'u', 's'))
* .putAll('c', Arrays.asList('h', 'e', 'r', 'r', 'y'))
* .build();
*
* // after deduplication, the resulting multimap is equivalent to
*
* static final ImmutableSetMultimap<Character, Character> FIRST_LETTER_MULTIMAP =
* ImmutableSetMultimap.<Character, Character>builder()
* .putAll('b', Arrays.asList('a', 'n'))
* .putAll('a', Arrays.asList('p', 'l', 'e', 's', 'a', 'r', 'g', 'u'))
* .putAll('c', Arrays.asList('a', 'r', 'o', 't', 'h', 'e', 'y'))
* .build();
* }
* }</pre>
*
* @since 21.0
*/
public static <T, K, V>
Collector<T, ?, ImmutableSetMultimap<K, V>> flatteningToImmutableSetMultimap(
Function<? super T, ? extends K> keyFunction,
Function<? super T, ? extends Stream<? extends V>> valuesFunction) {
return CollectCollectors.flatteningToImmutableSetMultimap(keyFunction, valuesFunction);
}
/**
* Returns the empty multimap.
*
* <p><b>Performance note:</b> the instance returned is a singleton.
*/
// Casting is safe because the multimap will never hold any elements.
@SuppressWarnings("unchecked")
public static <K, V> ImmutableSetMultimap<K, V> of() {
return (ImmutableSetMultimap<K, V>) EmptyImmutableSetMultimap.INSTANCE;
}
/** Returns an immutable multimap containing a single entry. */
public static <K, V> ImmutableSetMultimap<K, V> of(K k1, V v1) {
ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
builder.put(k1, v1);
return builder.build();
}
/**
* Returns an immutable multimap containing the given entries, in order. Repeated occurrences of
* an entry (according to {@link Object#equals}) after the first are ignored.
*/
public static <K, V> ImmutableSetMultimap<K, V> of(K k1, V v1, K k2, V v2) {
ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
builder.put(k1, v1);
builder.put(k2, v2);
return builder.build();
}
/**
* Returns an immutable multimap containing the given entries, in order. Repeated occurrences of
* an entry (according to {@link Object#equals}) after the first are ignored.
*/
public static <K, V> ImmutableSetMultimap<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3) {
ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
builder.put(k1, v1);
builder.put(k2, v2);
builder.put(k3, v3);
return builder.build();
}
/**
* Returns an immutable multimap containing the given entries, in order. Repeated occurrences of
* an entry (according to {@link Object#equals}) after the first are ignored.
*/
public static <K, V> ImmutableSetMultimap<K, V> of(
K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) {
ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
builder.put(k1, v1);
builder.put(k2, v2);
builder.put(k3, v3);
builder.put(k4, v4);
return builder.build();
}
/**
* Returns an immutable multimap containing the given entries, in order. Repeated occurrences of
* an entry (according to {@link Object#equals}) after the first are ignored.
*/
public static <K, V> ImmutableSetMultimap<K, V> of(
K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5) {
ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
builder.put(k1, v1);
builder.put(k2, v2);
builder.put(k3, v3);
builder.put(k4, v4);
builder.put(k5, v5);
return builder.build();
}
// looking for of() with > 5 entries? Use the builder instead.
/** Returns a new {@link Builder}. */
public static <K, V> Builder<K, V> builder() {
return new Builder<>();
}
/**
* A builder for creating immutable {@code SetMultimap} instances, especially {@code public static
* final} multimaps ("constant multimaps"). Example:
*
* <pre>{@code
* static final Multimap<String, Integer> STRING_TO_INTEGER_MULTIMAP =
* new ImmutableSetMultimap.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
*/
public static final class Builder<K, V> extends ImmutableMultimap.Builder<K, V> {
/**
* Creates a new builder. The returned builder is equivalent to the builder generated by {@link
* ImmutableSetMultimap#builder}.
*/
public Builder() {
super();
}
@Override
Collection<V> newMutableValueCollection() {
return Platform.preservesInsertionOrderOnAddsSet();
}
/** Adds a key-value mapping to the built multimap if it is not already present. */
@CanIgnoreReturnValue
@Override
public Builder<K, V> put(K key, V value) {
super.put(key, value);
return this;
}
/**
* Adds an entry to the built multimap if it is not already present.
*
* @since 11.0
*/
@CanIgnoreReturnValue
@Override
public Builder<K, V> put(Entry<? extends K, ? extends V> entry) {
super.put(entry);
return this;
}
/**
* {@inheritDoc}
*
* @since 19.0
*/
@CanIgnoreReturnValue
@Beta
@Override
public Builder<K, V> putAll(Iterable<? extends Entry<? extends K, ? extends V>> entries) {
super.putAll(entries);
return this;
}
@CanIgnoreReturnValue
@Override
public Builder<K, V> putAll(K key, Iterable<? extends V> values) {
super.putAll(key, values);
return this;
}
@CanIgnoreReturnValue
@Override
public Builder<K, V> putAll(K key, V... values) {
return putAll(key, Arrays.asList(values));
}
@CanIgnoreReturnValue
@Override
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;
}
@CanIgnoreReturnValue
@Override
Builder<K, V> combine(ImmutableMultimap.Builder<K, V> other) {
super.combine(other);
return this;
}
/**
* {@inheritDoc}
*
* @since 8.0
*/
@CanIgnoreReturnValue
@Override
public Builder<K, V> orderKeysBy(Comparator<? super K> keyComparator) {
super.orderKeysBy(keyComparator);
return this;
}
/**
* Specifies the ordering of the generated multimap's values for each key.
*
* <p>If this method is called, the sets returned by the {@code get()} method of the generated
* multimap and its {@link Multimap#asMap()} view are {@link ImmutableSortedSet} instances.
* However, serialization does not preserve that property, though it does maintain the key and
* value ordering.
*
* @since 8.0
*/
// TODO: Make serialization behavior consistent.
@CanIgnoreReturnValue
@Override
public Builder<K, V> orderValuesBy(Comparator<? super V> valueComparator) {
super.orderValuesBy(valueComparator);
return this;
}
/** Returns a newly-created immutable set multimap. */
@Override
public ImmutableSetMultimap<K, V> build() {
Collection<Map.Entry<K, Collection<V>>> mapEntries = builderMap.entrySet();
if (keyComparator != null) {
mapEntries = Ordering.from(keyComparator).<K>onKeys().immutableSortedCopy(mapEntries);
}
return fromMapEntries(mapEntries, valueComparator);
}
}
/**
* Returns an immutable set 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. Repeated occurrences of an entry in the multimap after the first are
* ignored.
*
* <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> ImmutableSetMultimap<K, V> copyOf(
Multimap<? extends K, ? extends V> multimap) {
return copyOf(multimap, null);
}
private static <K, V> ImmutableSetMultimap<K, V> copyOf(
Multimap<? extends K, ? extends V> multimap, Comparator<? super V> valueComparator) {
checkNotNull(multimap); // eager for GWT
if (multimap.isEmpty() && valueComparator == null) {
return of();
}
if (multimap instanceof ImmutableSetMultimap) {
@SuppressWarnings("unchecked") // safe since multimap is not writable
ImmutableSetMultimap<K, V> kvMultimap = (ImmutableSetMultimap<K, V>) multimap;
if (!kvMultimap.isPartialView()) {
return kvMultimap;
}
}
return fromMapEntries(multimap.asMap().entrySet(), valueComparator);
}
/**
* 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. If two values for the same key are {@linkplain
* Object#equals equal}, the first value encountered is used.
*
* @throws NullPointerException if any key, value, or entry is null
* @since 19.0
*/
@Beta
public static <K, V> ImmutableSetMultimap<K, V> copyOf(
Iterable<? extends Entry<? extends K, ? extends V>> entries) {
return new Builder<K, V>().putAll(entries).build();
}
/** Creates an ImmutableSetMultimap from an asMap.entrySet. */
static <K, V> ImmutableSetMultimap<K, V> fromMapEntries(
Collection<? extends Map.Entry<? extends K, ? extends Collection<? extends V>>> mapEntries,
@Nullable Comparator<? super V> valueComparator) {
if (mapEntries.isEmpty()) {
return of();
}
ImmutableMap.Builder<K, ImmutableSet<V>> builder =
new ImmutableMap.Builder<>(mapEntries.size());
int size = 0;
for (Entry<? extends K, ? extends Collection<? extends V>> entry : mapEntries) {
K key = entry.getKey();
Collection<? extends V> values = entry.getValue();
ImmutableSet<V> set = valueSet(valueComparator, values);
if (!set.isEmpty()) {
builder.put(key, set);
size += set.size();
}
}
return new ImmutableSetMultimap<>(builder.build(), size, valueComparator);
}
/**
* Returned by get() when a missing key is provided. Also holds the comparator, if any, used for
* values.
*/
private final transient ImmutableSet<V> emptySet;
ImmutableSetMultimap(
ImmutableMap<K, ImmutableSet<V>> map,
int size,
@Nullable Comparator<? super V> valueComparator) {
super(map, size);
this.emptySet = emptySet(valueComparator);
}
// views
/**
* Returns an immutable set of the values for the given key. If no mappings in the multimap have
* the provided key, an empty immutable set is returned. The values are in the same order as the
* parameters used to build this multimap.
*/
@Override
public ImmutableSet<V> get(@Nullable K key) {
// This cast is safe as its type is known in constructor.
ImmutableSet<V> set = (ImmutableSet<V>) map.get(key);
return MoreObjects.firstNonNull(set, emptySet);
}
@LazyInit @RetainedWith private transient @Nullable ImmutableSetMultimap<V, K> inverse;
/**
* {@inheritDoc}
*
* <p>Because an inverse of a set multimap cannot contain multiple pairs with the same key and
* value, this method returns an {@code ImmutableSetMultimap} rather than the {@code
* ImmutableMultimap} specified in the {@code ImmutableMultimap} class.
*/
@Override
public ImmutableSetMultimap<V, K> inverse() {
ImmutableSetMultimap<V, K> result = inverse;
return (result == null) ? (inverse = invert()) : result;
}
private ImmutableSetMultimap<V, K> invert() {
Builder<V, K> builder = builder();
for (Entry<K, V> entry : entries()) {
builder.put(entry.getValue(), entry.getKey());
}
ImmutableSetMultimap<V, K> invertedMultimap = builder.build();
invertedMultimap.inverse = this;
return invertedMultimap;
}
/**
* Guaranteed to throw an exception and leave the multimap unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@CanIgnoreReturnValue
@Deprecated
@Override
@DoNotCall("Always throws UnsupportedOperationException")
public final ImmutableSet<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
@DoNotCall("Always throws UnsupportedOperationException")
public final ImmutableSet<V> replaceValues(K key, Iterable<? extends V> values) {
throw new UnsupportedOperationException();
}
@LazyInit @RetainedWith private transient @Nullable ImmutableSet<Entry<K, V>> 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.
*/
@Override
public ImmutableSet<Entry<K, V>> entries() {
ImmutableSet<Entry<K, V>> result = entries;
return result == null ? (entries = new EntrySet<>(this)) : result;
}
private static final class EntrySet<K, V> extends ImmutableSet<Entry<K, V>> {
@Weak private final transient ImmutableSetMultimap<K, V> multimap;
EntrySet(ImmutableSetMultimap<K, V> multimap) {
this.multimap = multimap;
}
@Override
public boolean contains(@Nullable Object object) {
if (object instanceof Entry) {
Entry<?, ?> entry = (Entry<?, ?>) object;
return multimap.containsEntry(entry.getKey(), entry.getValue());
}
return false;
}
@Override
public int size() {
return multimap.size();
}
@Override
public UnmodifiableIterator<Entry<K, V>> iterator() {
return multimap.entryIterator();
}
@Override
boolean isPartialView() {
return false;
}
}
private static <V> ImmutableSet<V> valueSet(
@Nullable Comparator<? super V> valueComparator, Collection<? extends V> values) {
return (valueComparator == null)
? ImmutableSet.copyOf(values)
: ImmutableSortedSet.copyOf(valueComparator, values);
}
private static <V> ImmutableSet<V> emptySet(@Nullable Comparator<? super V> valueComparator) {
return (valueComparator == null)
? ImmutableSet.<V>of()
: ImmutableSortedSet.<V>emptySet(valueComparator);
}
private static <V> ImmutableSet.Builder<V> valuesBuilder(
@Nullable Comparator<? super V> valueComparator) {
return (valueComparator == null)
? new ImmutableSet.Builder<V>()
: new ImmutableSortedSet.Builder<V>(valueComparator);
}
/**
* @serialData number of distinct keys, and then for each distinct key: the key, the number of
* values for that key, and the key's values
*/
@GwtIncompatible // java.io.ObjectOutputStream
private void writeObject(ObjectOutputStream stream) throws IOException {
stream.defaultWriteObject();
stream.writeObject(valueComparator());
Serialization.writeMultimap(this, stream);
}
@Nullable
Comparator<? super V> valueComparator() {
return emptySet instanceof ImmutableSortedSet
? ((ImmutableSortedSet<V>) emptySet).comparator()
: null;
}
@GwtIncompatible // java serialization
private static final class SetFieldSettersHolder {
static final Serialization.FieldSetter<ImmutableSetMultimap> EMPTY_SET_FIELD_SETTER =
Serialization.getFieldSetter(ImmutableSetMultimap.class, "emptySet");
}
@GwtIncompatible // java.io.ObjectInputStream
// Serialization type safety is at the caller's mercy.
@SuppressWarnings("unchecked")
private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
stream.defaultReadObject();
Comparator<Object> valueComparator = (Comparator<Object>) stream.readObject();
int keyCount = stream.readInt();
if (keyCount < 0) {
throw new InvalidObjectException("Invalid key count " + keyCount);
}
ImmutableMap.Builder<Object, ImmutableSet<Object>> builder = ImmutableMap.builder();
int tmpSize = 0;
for (int i = 0; i < keyCount; i++) {
Object key = stream.readObject();
int valueCount = stream.readInt();
if (valueCount <= 0) {
throw new InvalidObjectException("Invalid value count " + valueCount);
}
ImmutableSet.Builder<Object> valuesBuilder = valuesBuilder(valueComparator);
for (int j = 0; j < valueCount; j++) {
valuesBuilder.add(stream.readObject());
}
ImmutableSet<Object> valueSet = valuesBuilder.build();
if (valueSet.size() != valueCount) {
throw new InvalidObjectException("Duplicate key-value pairs exist for key " + key);
}
builder.put(key, valueSet);
tmpSize += valueCount;
}
ImmutableMap<Object, ImmutableSet<Object>> tmpMap;
try {
tmpMap = builder.build();
} catch (IllegalArgumentException e) {
throw (InvalidObjectException) new InvalidObjectException(e.getMessage()).initCause(e);
}
FieldSettersHolder.MAP_FIELD_SETTER.set(this, tmpMap);
FieldSettersHolder.SIZE_FIELD_SETTER.set(this, tmpSize);
SetFieldSettersHolder.EMPTY_SET_FIELD_SETTER.set(this, emptySet(valueComparator));
}
@GwtIncompatible // not needed in emulated source.
private static final long serialVersionUID = 0;
}