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/*
* Copyright (C) 2008 Google Inc.
*
* 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.base.Nullable;
import com.google.common.collect.Serialization.FieldSetter;
import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.Collection;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
/**
* An immutable {@link ListMultimap} with reliable user-specified key and value
* iteration order. Does not permit null keys or values.
*
* Unlike {@link Multimaps#unmodifiableListMultimap(ListMultimap)}, which is
* a view of a separate map which can still change, an instance of
* {@code ImmutableMultimap} contains its own data and will never change.
* {@code ImmutableMultimap} 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.
*
* @author Jared Levy
*/
public class ImmutableMultimap
implements ListMultimap, Serializable {
private static ImmutableMultimap EMPTY_MULTIMAP
= new EmptyMultimap();
private static class EmptyMultimap extends ImmutableMultimap {
EmptyMultimap() {
super(ImmutableMap.>of(), 0);
}
@Override public boolean isEmpty() {
return true;
}
Object readResolve() {
return EMPTY_MULTIMAP; // preserve singleton property
}
private static final long serialVersionUID = 0;
}
/** Returns the empty multimap. */
// Casting is safe because the multimap will never hold any elements.
@SuppressWarnings("unchecked")
public static ImmutableMultimap empty() {
return (ImmutableMultimap) EMPTY_MULTIMAP;
}
/**
* 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();
}
/**
* Multimap for {@link ImmutableMultimap.Builder} that maintains key and value
* orderings, allows duplicate values, and performs better than
* {@link LinkedListMultimap}.
*/
private static class BuilderMultimap extends StandardMultimap {
BuilderMultimap() {
super(new LinkedHashMap>());
}
@Override Collection createCollection() {
return Lists.newArrayList();
}
private static final long serialVersionUID = 0;
}
/**
* A builder for creating immutable multimap instances, especially
* {@code public static final} multimaps ("constant multimaps"). Example:
* {@code
*
* static final Multimap STRING_TO_INTEGER_MULTIMAP =
* new ImmutableMultimap.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.
*/
public static class Builder {
private final Multimap builderMultimap = new BuilderMultimap();
/**
* Creates a new builder. The returned builder is equivalent to the builder
* generated by {@link ImmutableMultimap#builder}.
*/
public Builder() {}
/**
* Adds a key-value mapping to the built multimap.
*/
public Builder put(K key, V value) {
builderMultimap.put(checkNotNull(key), checkNotNull(value));
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.
*/
public Builder putAll(K key, Iterable values) {
Collection valueList = builderMultimap.get(checkNotNull(key));
for (V value : values) {
valueList.add(checkNotNull(value));
}
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. If a later
* value is null, earlier values may be added to the builder.
*/
public Builder putAll(K key, V... values) {
Collection valueList = builderMultimap.get(checkNotNull(key));
for (V value : values) {
valueList.add(checkNotNull(value));
}
return this;
}
public ImmutableMultimap build() {
return copyOf(builderMultimap);
}
}
/**
* 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.
*
* Note: Despite what the method name suggests, if
* {@code multimap} is an {@code ImmutableMultimap}, no copy will actually be
* performed, and the given map itself will be returned.
*
* @throws NullPointerException if any key or value in {@code multimap} is
* null
*/
public static ImmutableMultimap copyOf(
Multimap multimap) {
if (multimap.isEmpty()) {
return empty();
}
if (multimap instanceof ImmutableMultimap) {
@SuppressWarnings("unchecked") // safe since multimap is not writable
ImmutableMultimap kvMultimap = (ImmutableMultimap) multimap;
return kvMultimap;
}
ImmutableMap.Builder> builder = ImmutableMap.builder();
int size = 0;
for (Map.Entry> entry
: multimap.asMap().entrySet()) {
ImmutableList list = ImmutableList.copyOf(entry.getValue());
if (!list.isEmpty()) {
builder.put(entry.getKey(), list);
size += list.size();
}
}
return new ImmutableMultimap(builder.build(), size);
}
private final transient ImmutableMap> map;
private 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.
private static class FieldSettersHolder {
@SuppressWarnings("unchecked") // ImmutableMultimap raw type
static final FieldSetter MAP_FIELD_SETTER
= Serialization.getFieldSetter(ImmutableMultimap.class, "map");
@SuppressWarnings("unchecked") // ImmutableMultimap raw type
static final FieldSetter SIZE_FIELD_SETTER
= Serialization.getFieldSetter(ImmutableMultimap.class, "size");
}
private ImmutableMultimap(ImmutableMap> 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
*/
public List removeAll(Object key) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the multimap unmodified.
*
* @throws UnsupportedOperationException always
*/
public List replaceValues(K key, Iterable values) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the multimap unmodified.
*
* @throws UnsupportedOperationException always
*/
public void clear() {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the multimap unmodified.
*
* @throws UnsupportedOperationException always
*/
public boolean put(K key, V value) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the multimap unmodified.
*
* @throws UnsupportedOperationException always
*/
public boolean putAll(K key, Iterable values) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the multimap unmodified.
*
* @throws UnsupportedOperationException always
*/
public boolean putAll(Multimap multimap) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the multimap unmodified.
*
* @throws UnsupportedOperationException always
*/
public boolean remove(Object key, Object value) {
throw new UnsupportedOperationException();
}
// accessors
public boolean containsEntry(@Nullable Object key, @Nullable Object value) {
Collection valueList = map.get(key);
return (valueList != null) && valueList.contains(value);
}
public boolean containsKey(@Nullable Object key) {
return map.containsKey(key);
}
public boolean containsValue(@Nullable Object value) {
for (Collection valueList : map.values()) {
if (valueList.contains(value)) {
return true;
}
}
return false;
}
public boolean isEmpty() {
return false;
}
public int size() {
return size;
}
@Override public boolean equals(@Nullable Object object) {
if (object == this) {
return true;
}
if (object instanceof Multimap) {
Multimap that = (Multimap) object;
return this.map.equals(that.asMap());
}
return false;
}
@Override public int hashCode() {
return map.hashCode();
}
@Override public String toString() {
return map.toString();
}
// 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.
*/
public ImmutableList get(@Nullable K key) {
ImmutableList list = map.get(key);
return (list == null) ? ImmutableList.of() : list;
}
/**
* Returns an immutable set of the distinct keys in this multimap. These keys
* are ordered according to when they first appeared during the construction
* of this multimap.
*/
public ImmutableSet keySet() {
return map.keySet();
}
/**
* Returns an immutable map that associates each key with its corresponding
* values in the multimap. Though the method signature doesn't say so
* explicitly, the returned map has {@link ImmutableList} values.
*/
@SuppressWarnings("unchecked") // a widening cast
public ImmutableMap> asMap() {
return (ImmutableMap) map;
}
private transient ImmutableCollection> 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.
*/
public ImmutableCollection> entries() {
ImmutableCollection> result = entries;
return (result == null) ? (entries = new Entries(this)) : result;
}
private static class Entries
extends ImmutableCollection> {
final ImmutableMultimap multimap;
Entries(ImmutableMultimap multimap) {
this.multimap = multimap;
}
@Override public UnmodifiableIterator> iterator() {
final Iterator>> mapIterator
= multimap.map.entrySet().iterator();
return new UnmodifiableIterator>() {
Map.Entry> mapEntry;
int index;
public boolean hasNext() {
return ((mapEntry != null) && (index < mapEntry.getValue().size()))
|| mapIterator.hasNext();
}
public Map.Entry next() {
if ((mapEntry == null) || (index >= mapEntry.getValue().size())) {
mapEntry = mapIterator.next();
index = 0;
}
V value = mapEntry.getValue().get(index);
index++;
return Maps.immutableEntry(mapEntry.getKey(), value);
}
};
}
public int size() {
return multimap.size();
}
@Override public boolean contains(Object object) {
if (object instanceof Map.Entry) {
Map.Entry entry = (Map.Entry) object;
return multimap.containsEntry(entry.getKey(), entry.getValue());
}
return false;
}
private static final long serialVersionUID = 0;
}
private transient ImmutableMultiset keys;
/**
* Returns a collection, which may contain duplicates, of all keys. The number
* of times of key appears in the returned multiset equals the number of
* mappings the key has in the multimap. Duplicate keys appear consecutively
* in the multiset's iteration order.
*/
public ImmutableMultiset keys() {
ImmutableMultiset result = keys;
return (result == null)
? (keys = new ImmutableMultiset(new CountMap(this), size))
: result;
}
/*
* Map from key to value count, used to create the keys() multiset.
* Methods that ImmutableMultiset doesn't require are unsupported.
*/
private static class CountMap extends ImmutableMap {
final ImmutableMultimap multimap;
CountMap(ImmutableMultimap multimap) {
this.multimap = multimap;
}
@Override public boolean containsKey(Object key) {
return multimap.containsKey(key);
}
@Override public boolean containsValue(Object value) {
throw new UnsupportedOperationException();
}
@Override public Integer get(Object key) {
Collection valueList = multimap.map.get(key);
return (valueList == null) ? 0 : valueList.size();
}
@Override public ImmutableSet keySet() {
return multimap.keySet();
}
@Override public ImmutableCollection values() {
throw new UnsupportedOperationException();
}
public boolean isEmpty() {
return multimap.isEmpty();
}
public int size() {
return multimap.map.size();
}
transient ImmutableSet> entrySet;
@Override public ImmutableSet> entrySet() {
ImmutableSet> result = entrySet;
return (result == null)
? entrySet = new EntrySet(multimap) : result;
}
private static class EntrySet
extends ImmutableSet> {
final ImmutableMultimap multimap;
EntrySet(ImmutableMultimap multimap) {
this.multimap = multimap;
}
@Override public UnmodifiableIterator> iterator() {
final Iterator>> mapIterator
= multimap.map.entrySet().iterator();
return new UnmodifiableIterator>() {
public boolean hasNext() {
return mapIterator.hasNext();
}
public Entry next() {
Entry> entry = mapIterator.next();
return Maps.immutableEntry(entry.getKey(), entry.getValue().size());
}
};
}
public int size() {
return multimap.map.size();
}
private static final long serialVersionUID = 0;
}
private static final long serialVersionUID = 0;
}
private transient ImmutableCollection values;
/**
* 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.
*/
public ImmutableCollection values() {
ImmutableCollection v = values;
return (v == null) ? (values = new Values(this)) : v;
}
private static class Values extends ImmutableCollection {
final Multimap multimap;
Values(Multimap multimap) {
this.multimap = multimap;
}
@Override public UnmodifiableIterator iterator() {
final Iterator> entryIterator
= multimap.entries().iterator();
return new UnmodifiableIterator() {
public boolean hasNext() {
return entryIterator.hasNext();
}
public V next() {
return entryIterator.next().getValue();
}
};
}
public int size() {
return multimap.size();
}
private static final long serialVersionUID = 0;
}
/**
* @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
*/
private void writeObject(ObjectOutputStream stream) throws IOException {
stream.defaultWriteObject();
Serialization.writeMultimap(this, stream);
}
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);
}
Object[] array = new Object[valueCount];
for (int j = 0; j < valueCount; j++) {
array[j] = stream.readObject();
tmpSize += valueCount;
}
builder.put(key, ImmutableList.of(array));
}
ImmutableMap> 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);
}
private static final long serialVersionUID = 0;
}