com.google.common.collect.ImmutableListMultimap Maven / Gradle / Ivy
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/*
* 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 com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.base.Preconditions;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
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.Entry;
import java.util.function.Function;
import java.util.stream.Collector;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import javax.annotation.Nullable;
/**
* A {@link ListMultimap} whose contents will never change, with many other important properties
* detailed at {@link ImmutableCollection}.
*
* See the Guava User Guide article on
* immutable collections.
*
* @author Jared Levy
* @since 2.0
*/
@GwtCompatible(serializable = true, emulated = true)
public class ImmutableListMultimap extends ImmutableMultimap
implements ListMultimap {
/**
* 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.
*
* For streams with {@linkplain java.util.stream#Ordering defined encounter order}, that order
* is preserved, but entries are {@linkplain ImmutableMultimap#iteration grouped by key}.
*
* Example:
*
{@code
*
* static final Multimap 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 FIRST_LETTER_MULTIMAP =
* new ImmutableListMultimap.Builder()
* .put('b', "anana")
* .putAll('a', "pple", "sparagus")
* .putAll('c', "arrot", "herry")
* .build();}
*
* @since 21.0
*/
@Beta
public static Collector> toImmutableListMultimap(
Function keyFunction,
Function valueFunction) {
checkNotNull(keyFunction, "keyFunction");
checkNotNull(valueFunction, "valueFunction");
return Collector.of(
ImmutableListMultimap::builder,
(builder, t) -> builder.put(keyFunction.apply(t), valueFunction.apply(t)),
ImmutableListMultimap.Builder::combine,
ImmutableListMultimap.Builder::build);
}
/**
* 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.
*
* Example:
*
*
{@code
* static final ImmutableListMultimap 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 FIRST_LETTER_MULTIMAP =
* ImmutableListMultimap.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();
* }
* }
*
* @since 21.0
*/
@Beta
public static
Collector> flatteningToImmutableListMultimap(
Function keyFunction,
Function> valuesFunction) {
checkNotNull(keyFunction);
checkNotNull(valuesFunction);
return Collectors.collectingAndThen(
Multimaps.flatteningToMultimap(
input -> checkNotNull(keyFunction.apply(input)),
input -> valuesFunction.apply(input).peek(Preconditions::checkNotNull),
MultimapBuilder.linkedHashKeys().arrayListValues()::build),
ImmutableListMultimap::copyOf);
}
/** Returns the empty multimap. */
// Casting is safe because the multimap will never hold any elements.
@SuppressWarnings("unchecked")
public static ImmutableListMultimap of() {
return (ImmutableListMultimap) EmptyImmutableListMultimap.INSTANCE;
}
/**
* Returns an immutable multimap containing a single entry.
*/
public static ImmutableListMultimap of(K k1, V v1) {
ImmutableListMultimap.Builder builder = ImmutableListMultimap.builder();
builder.put(k1, v1);
return builder.build();
}
/**
* Returns an immutable multimap containing the given entries, in order.
*/
public static ImmutableListMultimap of(K k1, V v1, K k2, V v2) {
ImmutableListMultimap.Builder 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 ImmutableListMultimap of(K k1, V v1, K k2, V v2, K k3, V v3) {
ImmutableListMultimap.Builder 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 ImmutableListMultimap of(
K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) {
ImmutableListMultimap.Builder 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 ImmutableListMultimap of(
K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5) {
ImmutableListMultimap.Builder 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 Builder builder() {
return new Builder();
}
/**
* A builder for creating immutable {@code ListMultimap} instances, especially
* {@code public static final} multimaps ("constant multimaps"). Example:
* {@code
*
* static final Multimap STRING_TO_INTEGER_MULTIMAP =
* new ImmutableListMultimap.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.
*
* @since 2.0
*/
public static final class Builder extends ImmutableMultimap.Builder {
/**
* Creates a new builder. The returned builder is equivalent to the builder
* generated by {@link ImmutableListMultimap#builder}.
*/
public Builder() {}
@CanIgnoreReturnValue
@Override
public Builder put(K key, V value) {
super.put(key, value);
return this;
}
/**
* {@inheritDoc}
*
* @since 11.0
*/
@CanIgnoreReturnValue
@Override
public Builder put(Entry entry) {
super.put(entry);
return this;
}
/**
* {@inheritDoc}
*
* @since 19.0
*/
@CanIgnoreReturnValue
@Beta
@Override
public Builder putAll(Iterable> entries) {
super.putAll(entries);
return this;
}
@CanIgnoreReturnValue
@Override
public Builder putAll(K key, Iterable values) {
super.putAll(key, values);
return this;
}
@CanIgnoreReturnValue
@Override
public Builder putAll(K key, V... values) {
super.putAll(key, values);
return this;
}
@CanIgnoreReturnValue
@Override
public Builder putAll(Multimap multimap) {
super.putAll(multimap);
return this;
}
@CanIgnoreReturnValue
@Override
Builder combine(ImmutableMultimap.Builder other) {
super.combine(other);
return this;
}
/**
* {@inheritDoc}
*
* @since 8.0
*/
@CanIgnoreReturnValue
@Override
public Builder orderKeysBy(Comparator keyComparator) {
super.orderKeysBy(keyComparator);
return this;
}
/**
* {@inheritDoc}
*
* @since 8.0
*/
@CanIgnoreReturnValue
@Override
public Builder orderValuesBy(Comparator valueComparator) {
super.orderValuesBy(valueComparator);
return this;
}
/**
* Returns a newly-created immutable list multimap.
*/
@Override
public ImmutableListMultimap build() {
return (ImmutableListMultimap) 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.
*
* 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 ImmutableListMultimap copyOf(
Multimap 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 kvMultimap = (ImmutableListMultimap) multimap;
if (!kvMultimap.isPartialView()) {
return kvMultimap;
}
}
ImmutableMap.Builder> builder =
new ImmutableMap.Builder>(multimap.asMap().size());
int size = 0;
for (Entry> entry :
multimap.asMap().entrySet()) {
ImmutableList list = ImmutableList.copyOf(entry.getValue());
if (!list.isEmpty()) {
builder.put(entry.getKey(), list);
size += list.size();
}
}
return new ImmutableListMultimap(builder.build(), size);
}
/**
* 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 ImmutableListMultimap copyOf(
Iterable> entries) {
return new Builder().putAll(entries).build();
}
ImmutableListMultimap(ImmutableMap> 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 get(@Nullable K key) {
// This cast is safe as its type is known in constructor.
ImmutableList list = (ImmutableList) map.get(key);
return (list == null) ? ImmutableList.of() : list;
}
@LazyInit
@RetainedWith
private transient ImmutableListMultimap inverse;
/**
* {@inheritDoc}
*
* 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 inverse() {
ImmutableListMultimap result = inverse;
return (result == null) ? (inverse = invert()) : result;
}
private ImmutableListMultimap invert() {
Builder builder = builder();
for (Entry entry : entries()) {
builder.put(entry.getValue(), entry.getKey());
}
ImmutableListMultimap 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
public ImmutableList 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 ImmutableList replaceValues(K key, Iterable 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> 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