ImmutableListMultimap.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 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.DoNotCall;
import com.google.errorprone.annotations.concurrent.LazyInit;
import com.google.j2objc.annotations.RetainedWith;
import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
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 ListMultimap} whose contents will never change, with many other important properties
* detailed at {@link ImmutableCollection}.
*
* <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(serializable = true, emulated = true)
public class ImmutableListMultimap<K, V> extends ImmutableMultimap<K, V>
implements ListMultimap<K, V> {
/**
* Returns a {@link Collector} that accumulates elements into an {@code ImmutableListMultimap}
* 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(toImmutableListMultimap(str -> str.charAt(0), str -> str.substring(1)));
*
* // is equivalent to
*
* static final Multimap<Character, String> FIRST_LETTER_MULTIMAP =
* new ImmutableListMultimap.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, ?, ImmutableListMultimap<K, V>> toImmutableListMultimap(
Function<? super T, ? extends K> keyFunction,
Function<? super T, ? extends V> valueFunction) {
return CollectCollectors.toImmutableListMultimap(keyFunction, valueFunction);
}
/**
* Returns a {@code Collector} accumulating entries into an {@code ImmutableListMultimap}. 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 ImmutableListMultimap<Character, Character> FIRST_LETTER_MULTIMAP =
* Stream.of("banana", "apple", "carrot", "asparagus", "cherry")
* .collect(
* flatteningToImmutableListMultimap(
* str -> str.charAt(0),
* str -> str.substring(1).chars().mapToObj(c -> (char) c));
*
* // is equivalent to
*
* static final ImmutableListMultimap<Character, Character> FIRST_LETTER_MULTIMAP =
* ImmutableListMultimap.<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();
* }
* }</pre>
*
* @since 21.0
*/
public static <T, K, V>
Collector<T, ?, ImmutableListMultimap<K, V>> flatteningToImmutableListMultimap(
Function<? super T, ? extends K> keyFunction,
Function<? super T, ? extends Stream<? extends V>> valuesFunction) {
return CollectCollectors.flatteningToImmutableListMultimap(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> ImmutableListMultimap<K, V> of() {
return (ImmutableListMultimap<K, V>) EmptyImmutableListMultimap.INSTANCE;
}
/** Returns an immutable multimap containing a single entry. */
public static <K, V> ImmutableListMultimap<K, V> of(K k1, V v1) {
ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap.builder();
builder.put(k1, v1);
return builder.build();
}
/** Returns an immutable multimap containing the given entries, in order. */
public static <K, V> ImmutableListMultimap<K, V> of(K k1, V v1, K k2, V v2) {
ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap.builder();
builder.put(k1, v1);
builder.put(k2, v2);
return builder.build();
}
/** Returns an immutable multimap containing the given entries, in order. */
public static <K, V> ImmutableListMultimap<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3) {
ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap.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. */
public static <K, V> ImmutableListMultimap<K, V> of(
K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) {
ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap.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. */
public static <K, V> ImmutableListMultimap<K, V> of(
K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5) {
ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap.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 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 {@code ListMultimap} instances, especially {@code public
* static final} multimaps ("constant multimaps"). Example:
*
* <pre>{@code
* static final Multimap<String, Integer> STRING_TO_INTEGER_MULTIMAP =
* new ImmutableListMultimap.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
* ImmutableListMultimap#builder}.
*/
public Builder() {}
@CanIgnoreReturnValue
@Override
public Builder<K, V> put(K key, V value) {
super.put(key, value);
return this;
}
/**
* {@inheritDoc}
*
* @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) {
super.putAll(key, values);
return this;
}
@CanIgnoreReturnValue
@Override
public Builder<K, V> putAll(Multimap<? extends K, ? extends V> multimap) {
super.putAll(multimap);
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;
}
/**
* {@inheritDoc}
*
* @since 8.0
*/
@CanIgnoreReturnValue
@Override
public Builder<K, V> orderValuesBy(Comparator<? super V> valueComparator) {
super.orderValuesBy(valueComparator);
return this;
}
/** Returns a newly-created immutable list multimap. */
@Override
public ImmutableListMultimap<K, V> build() {
return (ImmutableListMultimap<K, V>) super.build();
}
}
/**
* 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.
*
* <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> ImmutableListMultimap<K, V> copyOf(
Multimap<? extends K, ? extends V> multimap) {
if (multimap.isEmpty()) {
return of();
}
// TODO(lowasser): copy ImmutableSetMultimap by using asList() on the sets
if (multimap instanceof ImmutableListMultimap) {
@SuppressWarnings("unchecked") // safe since multimap is not writable
ImmutableListMultimap<K, V> kvMultimap = (ImmutableListMultimap<K, V>) multimap;
if (!kvMultimap.isPartialView()) {
return kvMultimap;
}
}
return fromMapEntries(multimap.asMap().entrySet(), null);
}
/**
* 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> ImmutableListMultimap<K, V> copyOf(
Iterable<? extends Entry<? extends K, ? extends V>> entries) {
return new Builder<K, V>().putAll(entries).build();
}
/** Creates an ImmutableListMultimap from an asMap.entrySet. */
static <K, V> ImmutableListMultimap<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, ImmutableList<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();
ImmutableList<V> list =
(valueComparator == null)
? ImmutableList.copyOf(values)
: ImmutableList.sortedCopyOf(valueComparator, values);
if (!list.isEmpty()) {
builder.put(key, list);
size += list.size();
}
}
return new ImmutableListMultimap<>(builder.build(), size);
}
ImmutableListMultimap(ImmutableMap<K, ImmutableList<V>> map, int size) {
super(map, size);
}
// views
/**
* Returns an immutable list of the values for the given key. If no mappings in the multimap have
* the provided key, an empty immutable list is returned. The values are in the same order as the
* parameters used to build this multimap.
*/
@Override
public ImmutableList<V> get(@Nullable K key) {
// This cast is safe as its type is known in constructor.
ImmutableList<V> list = (ImmutableList<V>) map.get(key);
return (list == null) ? ImmutableList.<V>of() : list;
}
@LazyInit @RetainedWith private transient ImmutableListMultimap<V, K> inverse;
/**
* {@inheritDoc}
*
* <p>Because an inverse of a list multimap can contain multiple pairs with the same key and
* value, this method returns an {@code ImmutableListMultimap} rather than the {@code
* ImmutableMultimap} specified in the {@code ImmutableMultimap} class.
*
* @since 11.0
*/
@Override
public ImmutableListMultimap<V, K> inverse() {
ImmutableListMultimap<V, K> result = inverse;
return (result == null) ? (inverse = invert()) : result;
}
private ImmutableListMultimap<V, K> invert() {
Builder<V, K> builder = builder();
for (Entry<K, V> entry : entries()) {
builder.put(entry.getValue(), entry.getKey());
}
ImmutableListMultimap<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 ImmutableList<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 ImmutableList<V> replaceValues(K key, Iterable<? extends V> values) {
throw new UnsupportedOperationException();
}
/**
* @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();
Serialization.writeMultimap(this, stream);
}
@GwtIncompatible // java.io.ObjectInputStream
private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
stream.defaultReadObject();
int keyCount = stream.readInt();
if (keyCount < 0) {
throw new InvalidObjectException("Invalid key count " + keyCount);
}
ImmutableMap.Builder<Object, ImmutableList<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);
}
ImmutableList.Builder<Object> valuesBuilder = ImmutableList.builder();
for (int j = 0; j < valueCount; j++) {
valuesBuilder.add(stream.readObject());
}
builder.put(key, valuesBuilder.build());
tmpSize += valueCount;
}
ImmutableMap<Object, ImmutableList<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);
}
@GwtIncompatible // Not needed in emulated source
private static final long serialVersionUID = 0;
}