com.google.common.collect.ImmutableSetMultimap Maven / Gradle / Ivy
/*
* 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 static java.util.Arrays.asList;
import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.base.MoreObjects;
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.Collections;
import java.util.Comparator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import javax.annotation.Nullable;
/**
* An immutable {@link SetMultimap} with reliable user-specified key and value
* iteration order. Does not permit null keys or values.
*
* Unlike {@link Multimaps#unmodifiableSetMultimap(SetMultimap)}, which is
* a view of a separate multimap which can still change, an instance of
* {@code ImmutableSetMultimap} contains its own data and will never
* change. {@code ImmutableSetMultimap} 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.
*
*
See the Guava User Guide article on
* immutable collections.
*
* @author Mike Ward
* @since 2.0 (imported from Google Collections Library)
*/
@GwtCompatible(serializable = true, emulated = true)
public class ImmutableSetMultimap
extends ImmutableMultimap
implements SetMultimap {
/** Returns the empty multimap. */
// Casting is safe because the multimap will never hold any elements.
@SuppressWarnings("unchecked")
public static ImmutableSetMultimap of() {
return (ImmutableSetMultimap) EmptyImmutableSetMultimap.INSTANCE;
}
/**
* Returns an immutable multimap containing a single entry.
*/
public static ImmutableSetMultimap of(K k1, V v1) {
ImmutableSetMultimap.Builder 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 ImmutableSetMultimap of(K k1, V v1, K k2, V v2) {
ImmutableSetMultimap.Builder 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 ImmutableSetMultimap of(
K k1, V v1, K k2, V v2, K k3, V v3) {
ImmutableSetMultimap.Builder 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 ImmutableSetMultimap of(
K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) {
ImmutableSetMultimap.Builder 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 ImmutableSetMultimap of(
K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5) {
ImmutableSetMultimap.Builder 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 Builder builder() {
return new Builder();
}
/**
* Multimap for {@link ImmutableSetMultimap.Builder} that maintains key
* and value orderings and performs better than {@link LinkedHashMultimap}.
*/
private static class BuilderMultimap extends AbstractMapBasedMultimap {
BuilderMultimap() {
super(new LinkedHashMap>());
}
@Override Collection createCollection() {
return Sets.newLinkedHashSet();
}
private static final long serialVersionUID = 0;
}
/**
* A builder for creating immutable {@code SetMultimap} instances, especially
* {@code public static final} multimaps ("constant multimaps"). Example:
* {@code
*
* static final Multimap STRING_TO_INTEGER_MULTIMAP =
* new ImmutableSetMultimap.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 (imported from Google Collections Library)
*/
public static final class Builder
extends ImmutableMultimap.Builder {
/**
* Creates a new builder. The returned builder is equivalent to the builder
* generated by {@link ImmutableSetMultimap#builder}.
*/
public Builder() {
builderMultimap = new BuilderMultimap();
}
/**
* Adds a key-value mapping to the built multimap if it is not already
* present.
*/
@Override public Builder put(K key, V value) {
builderMultimap.put(checkNotNull(key), checkNotNull(value));
return this;
}
/**
* Adds an entry to the built multimap if it is not already present.
*
* @since 11.0
*/
@Override public Builder put(Entry entry) {
builderMultimap.put(
checkNotNull(entry.getKey()), checkNotNull(entry.getValue()));
return this;
}
@Override public Builder putAll(K key, Iterable values) {
Collection collection = builderMultimap.get(checkNotNull(key));
for (V value : values) {
collection.add(checkNotNull(value));
}
return this;
}
@Override public Builder putAll(K key, V... values) {
return putAll(key, Arrays.asList(values));
}
@Override public Builder putAll(
Multimap multimap) {
for (Entry> entry
: multimap.asMap().entrySet()) {
putAll(entry.getKey(), entry.getValue());
}
return this;
}
/**
* {@inheritDoc}
*
* @since 8.0
*/
@Override
public Builder orderKeysBy(Comparator keyComparator) {
this.keyComparator = checkNotNull(keyComparator);
return this;
}
/**
* Specifies the ordering of the generated multimap's values for each key.
*
* 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.
@Override
public Builder orderValuesBy(Comparator valueComparator) {
super.orderValuesBy(valueComparator);
return this;
}
/**
* Returns a newly-created immutable set multimap.
*/
@Override public ImmutableSetMultimap build() {
if (keyComparator != null) {
Multimap sortedCopy = new BuilderMultimap();
List>> entries = Lists.newArrayList(
builderMultimap.asMap().entrySet());
Collections.sort(
entries,
Ordering.from(keyComparator).onKeys());
for (Map.Entry> entry : entries) {
sortedCopy.putAll(entry.getKey(), entry.getValue());
}
builderMultimap = sortedCopy;
}
return copyOf(builderMultimap, 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.
*
* 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 ImmutableSetMultimap copyOf(
Multimap multimap) {
return copyOf(multimap, null);
}
private static ImmutableSetMultimap copyOf(
Multimap multimap,
Comparator 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 kvMultimap
= (ImmutableSetMultimap) multimap;
if (!kvMultimap.isPartialView()) {
return kvMultimap;
}
}
ImmutableMap.Builder> builder = ImmutableMap.builder();
int size = 0;
for (Entry> entry
: multimap.asMap().entrySet()) {
K key = entry.getKey();
Collection values = entry.getValue();
ImmutableSet 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 emptySet;
ImmutableSetMultimap(ImmutableMap> map, int size,
@Nullable Comparator 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 get(@Nullable K key) {
// This cast is safe as its type is known in constructor.
ImmutableSet set = (ImmutableSet) map.get(key);
return MoreObjects.firstNonNull(set, emptySet);
}
private transient ImmutableSetMultimap inverse;
/**
* {@inheritDoc}
*
* 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.
*
* @since 11.0
*/
public ImmutableSetMultimap inverse() {
ImmutableSetMultimap result = inverse;
return (result == null) ? (inverse = invert()) : result;
}
private ImmutableSetMultimap invert() {
Builder builder = builder();
for (Entry entry : entries()) {
builder.put(entry.getValue(), entry.getKey());
}
ImmutableSetMultimap invertedMultimap = builder.build();
invertedMultimap.inverse = this;
return invertedMultimap;
}
/**
* Guaranteed to throw an exception and leave the multimap unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated @Override public ImmutableSet removeAll(Object key) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the multimap unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated @Override public ImmutableSet replaceValues(
K key, Iterable values) {
throw new UnsupportedOperationException();
}
private transient ImmutableSet> 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> entries() {
ImmutableSet> result = entries;
return (result == null)
? (entries = new EntrySet(this))
: result;
}
private static final class EntrySet extends ImmutableSet> {
private transient final ImmutableSetMultimap multimap;
EntrySet(ImmutableSetMultimap 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> iterator() {
return multimap.entryIterator();
}
@Override
boolean isPartialView() {
return false;
}
}
private static ImmutableSet valueSet(
@Nullable Comparator valueComparator,
Collection values) {
return (valueComparator == null)
? ImmutableSet.copyOf(values)
: ImmutableSortedSet.copyOf(valueComparator, values);
}
private static ImmutableSet emptySet(
@Nullable Comparator valueComparator) {
return (valueComparator == null)
? ImmutableSet.of()
: ImmutableSortedSet.emptySet(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 valueComparator() {
return emptySet instanceof ImmutableSortedSet
? ((ImmutableSortedSet) emptySet).comparator()
: null;
}
@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