com.google.common.collect.LinkedHashMultimap Maven / Gradle / Ivy
/*
* Copyright (C) 2007 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 com.google.common.base.Preconditions.checkState;
import static com.google.common.collect.CollectPreconditions.checkNonnegative;
import static java.util.Objects.requireNonNull;
import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Objects;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.j2objc.annotations.WeakOuter;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Arrays;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.function.Consumer;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* Implementation of {@code Multimap} that does not allow duplicate key-value entries and that
* returns collections whose iterators follow the ordering in which the data was added to the
* multimap.
*
* The collections returned by {@code keySet}, {@code keys}, and {@code asMap} iterate through
* the keys in the order they were first added to the multimap. Similarly, {@code get}, {@code
* removeAll}, and {@code replaceValues} return collections that iterate through the values in the
* order they were added. The collections generated by {@code entries} and {@code values} iterate
* across the key-value mappings in the order they were added to the multimap.
*
*
The iteration ordering of the collections generated by {@code keySet}, {@code keys}, and
* {@code asMap} has a few subtleties. As long as the set of keys remains unchanged, adding or
* removing mappings does not affect the key iteration order. However, if you remove all values
* associated with a key and then add the key back to the multimap, that key will come last in the
* key iteration order.
*
*
The multimap does not store duplicate key-value pairs. Adding a new key-value pair equal to an
* existing key-value pair has no effect.
*
*
Keys and values may be null. All optional multimap methods are supported, and all returned
* views are modifiable.
*
*
This class is not threadsafe when any concurrent operations update the multimap. Concurrent
* read operations will work correctly. To allow concurrent update operations, wrap your multimap
* with a call to {@link Multimaps#synchronizedSetMultimap}.
*
*
Warning: Do not modify either a key or a value of a {@code LinkedHashMultimap}
* in a way that affects its {@link Object#equals} behavior. Undefined behavior and bugs will
* result.
*
*
See the Guava User Guide article on {@code Multimap}.
*
* @author Jared Levy
* @author Louis Wasserman
* @since 2.0
*/
@GwtCompatible(serializable = true, emulated = true)
@ElementTypesAreNonnullByDefault
public final class LinkedHashMultimap
extends LinkedHashMultimapGwtSerializationDependencies {
/** Creates a new, empty {@code LinkedHashMultimap} with the default initial capacities. */
public static
LinkedHashMultimap create() {
return new LinkedHashMultimap<>(DEFAULT_KEY_CAPACITY, DEFAULT_VALUE_SET_CAPACITY);
}
/**
* Constructs an empty {@code LinkedHashMultimap} with enough capacity to hold the specified
* numbers of keys and values without rehashing.
*
* @param expectedKeys the expected number of distinct keys
* @param expectedValuesPerKey the expected average number of values per key
* @throws IllegalArgumentException if {@code expectedKeys} or {@code expectedValuesPerKey} is
* negative
*/
public static
LinkedHashMultimap create(int expectedKeys, int expectedValuesPerKey) {
return new LinkedHashMultimap<>(
Maps.capacity(expectedKeys), Maps.capacity(expectedValuesPerKey));
}
/**
* Constructs a {@code LinkedHashMultimap} with the same mappings as the specified multimap. If a
* key-value mapping appears multiple times in the input multimap, it only appears once in the
* constructed multimap. The new multimap has the same {@link Multimap#entries()} iteration order
* as the input multimap, except for excluding duplicate mappings.
*
* @param multimap the multimap whose contents are copied to this multimap
*/
public static
LinkedHashMultimap create(Multimap multimap) {
LinkedHashMultimap result = create(multimap.keySet().size(), DEFAULT_VALUE_SET_CAPACITY);
result.putAll(multimap);
return result;
}
private interface ValueSetLink {
ValueSetLink getPredecessorInValueSet();
ValueSetLink getSuccessorInValueSet();
void setPredecessorInValueSet(ValueSetLink entry);
void setSuccessorInValueSet(ValueSetLink entry);
}
private static void succeedsInValueSet(
ValueSetLink pred, ValueSetLink succ) {
pred.setSuccessorInValueSet(succ);
succ.setPredecessorInValueSet(pred);
}
private static void succeedsInMultimap(
ValueEntry pred, ValueEntry succ) {
pred.setSuccessorInMultimap(succ);
succ.setPredecessorInMultimap(pred);
}
private static void deleteFromValueSet(
ValueSetLink entry) {
succeedsInValueSet(entry.getPredecessorInValueSet(), entry.getSuccessorInValueSet());
}
private static void deleteFromMultimap(
ValueEntry entry) {
succeedsInMultimap(entry.getPredecessorInMultimap(), entry.getSuccessorInMultimap());
}
/**
* LinkedHashMultimap entries are in no less than three coexisting linked lists: a bucket in the
* hash table for a {@code Set} associated with a key, the linked list of insertion-ordered
* entries in that {@code Set}, and the linked list of entries in the LinkedHashMultimap as a
* whole.
*/
@VisibleForTesting
static final class ValueEntry
extends ImmutableEntry implements ValueSetLink {
final int smearedValueHash;
@CheckForNull ValueEntry nextInValueBucket;
/*
* The *InValueSet and *InMultimap fields below are null after construction, but we almost
* always call succeedsIn*() to initialize them immediately thereafter.
*
* The exception is the *InValueSet fields of multimapHeaderEntry, which are never set. (That
* works out fine as long as we continue to be careful not to try to delete them or iterate
* past them.)
*
* We could consider "lying" and omitting @CheckNotNull from all these fields. Normally, I'm not
* a fan of that: What if we someday implement (presumably to be enabled during tests only)
* bytecode rewriting that checks for any null value that passes through an API with a
* known-non-null type? But that particular problem might not arise here, since we're not
* actually reading from the fields in any case in which they might be null (as proven by the
* requireNonNull checks below). Plus, we're *already* lying here, since newHeader passes a null
* key and value, which we pass to the superconstructor, even though the key and value type for
* a given entry might not include null. The right fix for the header problems is probably to
* define a separate MultimapLink interface with a separate "header" implementation, which
* hopefully could avoid implementing Entry or ValueSetLink at all. (But note that that approach
* requires us to define extra classes -- unfortunate under Android.) *Then* we could consider
* lying about the fields below on the grounds that we always initialize them just after the
* constructor -- an example of the kind of lying that our hypothetical bytecode rewriter would
* already have to deal with, thanks to DI frameworks that perform field and method injection,
* frameworks like Android that define post-construct hooks like Activity.onCreate, etc.
*/
@CheckForNull ValueSetLink predecessorInValueSet;
@CheckForNull ValueSetLink successorInValueSet;
@CheckForNull ValueEntry predecessorInMultimap;
@CheckForNull ValueEntry successorInMultimap;
ValueEntry(
@ParametricNullness K key,
@ParametricNullness V value,
int smearedValueHash,
@CheckForNull ValueEntry nextInValueBucket) {
super(key, value);
this.smearedValueHash = smearedValueHash;
this.nextInValueBucket = nextInValueBucket;
}
@SuppressWarnings("nullness") // see the comment on the class fields, especially about newHeader
static ValueEntry newHeader() {
return new ValueEntry<>(null, null, 0, null);
}
boolean matchesValue(@CheckForNull Object v, int smearedVHash) {
return smearedValueHash == smearedVHash && Objects.equal(getValue(), v);
}
@Override
public ValueSetLink getPredecessorInValueSet() {
return requireNonNull(predecessorInValueSet); // see the comment on the class fields
}
@Override
public ValueSetLink getSuccessorInValueSet() {
return requireNonNull(successorInValueSet); // see the comment on the class fields
}
@Override
public void setPredecessorInValueSet(ValueSetLink entry) {
predecessorInValueSet = entry;
}
@Override
public void setSuccessorInValueSet(ValueSetLink entry) {
successorInValueSet = entry;
}
public ValueEntry getPredecessorInMultimap() {
return requireNonNull(predecessorInMultimap); // see the comment on the class fields
}
public ValueEntry getSuccessorInMultimap() {
return requireNonNull(successorInMultimap); // see the comment on the class fields
}
public void setSuccessorInMultimap(ValueEntry multimapSuccessor) {
this.successorInMultimap = multimapSuccessor;
}
public void setPredecessorInMultimap(ValueEntry multimapPredecessor) {
this.predecessorInMultimap = multimapPredecessor;
}
}
private static final int DEFAULT_KEY_CAPACITY = 16;
private static final int DEFAULT_VALUE_SET_CAPACITY = 2;
@VisibleForTesting static final double VALUE_SET_LOAD_FACTOR = 1.0;
@VisibleForTesting transient int valueSetCapacity = DEFAULT_VALUE_SET_CAPACITY;
private transient ValueEntry multimapHeaderEntry;
private LinkedHashMultimap(int keyCapacity, int valueSetCapacity) {
super(Platform.>newLinkedHashMapWithExpectedSize(keyCapacity));
checkNonnegative(valueSetCapacity, "expectedValuesPerKey");
this.valueSetCapacity = valueSetCapacity;
this.multimapHeaderEntry = ValueEntry.newHeader();
succeedsInMultimap(multimapHeaderEntry, multimapHeaderEntry);
}
/**
* {@inheritDoc}
*
* Creates an empty {@code LinkedHashSet} for a collection of values for one key.
*
* @return a new {@code LinkedHashSet} containing a collection of values for one key
*/
@Override
Set createCollection() {
return Platform.newLinkedHashSetWithExpectedSize(valueSetCapacity);
}
/**
* {@inheritDoc}
*
* Creates a decorated insertion-ordered set that also keeps track of the order in which
* key-value pairs are added to the multimap.
*
* @param key key to associate with values in the collection
* @return a new decorated set containing a collection of values for one key
*/
@Override
Collection createCollection(@ParametricNullness K key) {
return new ValueSet(key, valueSetCapacity);
}
/**
* {@inheritDoc}
*
* If {@code values} is not empty and the multimap already contains a mapping for {@code key},
* the {@code keySet()} ordering is unchanged. However, the provided values always come last in
* the {@link #entries()} and {@link #values()} iteration orderings.
*/
@CanIgnoreReturnValue
@Override
public Set replaceValues(@ParametricNullness K key, Iterable values) {
return super.replaceValues(key, values);
}
/**
* Returns a set of all key-value pairs. Changes to the returned set will update the underlying
* multimap, and vice versa. The entries set does not support the {@code add} or {@code addAll}
* operations.
*
* The iterator generated by the returned set traverses the entries in the order they were
* added to the multimap.
*
*
Each entry is an immutable snapshot of a key-value mapping in the multimap, taken at the
* time the entry is returned by a method call to the collection or its iterator.
*/
@Override
public Set> entries() {
return super.entries();
}
/**
* Returns a view collection of all distinct keys contained in this multimap. Note that the
* key set contains a key if and only if this multimap maps that key to at least one value.
*
* The iterator generated by the returned set traverses the keys in the order they were first
* added to the multimap.
*
*
Changes to the returned set will update the underlying multimap, and vice versa. However,
* adding to the returned set is not possible.
*/
@Override
public Set keySet() {
return super.keySet();
}
/**
* Returns a collection of all values in the multimap. Changes to the returned collection will
* update the underlying multimap, and vice versa.
*
* The iterator generated by the returned collection traverses the values in the order they
* were added to the multimap.
*/
@Override
public Collection values() {
return super.values();
}
@VisibleForTesting
@WeakOuter
final class ValueSet extends Sets.ImprovedAbstractSet implements ValueSetLink {
/*
* We currently use a fixed load factor of 1.0, a bit higher than normal to reduce memory
* consumption.
*/
@ParametricNullness private final K key;
@VisibleForTesting @Nullable ValueEntry[] hashTable;
private int size = 0;
private int modCount = 0;
// We use the set object itself as the end of the linked list, avoiding an unnecessary
// entry object per key.
private ValueSetLink firstEntry;
private ValueSetLink lastEntry;
ValueSet(@ParametricNullness K key, int expectedValues) {
this.key = key;
this.firstEntry = this;
this.lastEntry = this;
// Round expected values up to a power of 2 to get the table size.
int tableSize = Hashing.closedTableSize(expectedValues, VALUE_SET_LOAD_FACTOR);
@SuppressWarnings({"rawtypes", "unchecked"})
@Nullable
ValueEntry[] hashTable = new @Nullable ValueEntry[tableSize];
this.hashTable = hashTable;
}
private int mask() {
return hashTable.length - 1;
}
@Override
public ValueSetLink getPredecessorInValueSet() {
return lastEntry;
}
@Override
public ValueSetLink getSuccessorInValueSet() {
return firstEntry;
}
@Override
public void setPredecessorInValueSet(ValueSetLink entry) {
lastEntry = entry;
}
@Override
public void setSuccessorInValueSet(ValueSetLink entry) {
firstEntry = entry;
}
@Override
public Iterator iterator() {
return new Iterator() {
ValueSetLink nextEntry = firstEntry;
@CheckForNull ValueEntry toRemove;
int expectedModCount = modCount;
private void checkForComodification() {
if (modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
}
@Override
public boolean hasNext() {
checkForComodification();
return nextEntry != ValueSet.this;
}
@Override
@ParametricNullness
public V next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
ValueEntry entry = (ValueEntry) nextEntry;
V result = entry.getValue();
toRemove = entry;
nextEntry = entry.getSuccessorInValueSet();
return result;
}
@Override
public void remove() {
checkForComodification();
checkState(toRemove != null, "no calls to next() since the last call to remove()");
ValueSet.this.remove(toRemove.getValue());
expectedModCount = modCount;
toRemove = null;
}
};
}
@Override
public void forEach(Consumer action) {
checkNotNull(action);
for (ValueSetLink entry = firstEntry;
entry != ValueSet.this;
entry = entry.getSuccessorInValueSet()) {
action.accept(((ValueEntry) entry).getValue());
}
}
@Override
public int size() {
return size;
}
@Override
public boolean contains(@CheckForNull Object o) {
int smearedHash = Hashing.smearedHash(o);
for (ValueEntry entry = hashTable[smearedHash & mask()];
entry != null;
entry = entry.nextInValueBucket) {
if (entry.matchesValue(o, smearedHash)) {
return true;
}
}
return false;
}
@Override
public boolean add(@ParametricNullness V value) {
int smearedHash = Hashing.smearedHash(value);
int bucket = smearedHash & mask();
ValueEntry rowHead = hashTable[bucket];
for (ValueEntry entry = rowHead; entry != null; entry = entry.nextInValueBucket) {
if (entry.matchesValue(value, smearedHash)) {
return false;
}
}
ValueEntry newEntry = new ValueEntry<>(key, value, smearedHash, rowHead);
succeedsInValueSet(lastEntry, newEntry);
succeedsInValueSet(newEntry, this);
succeedsInMultimap(multimapHeaderEntry.getPredecessorInMultimap(), newEntry);
succeedsInMultimap(newEntry, multimapHeaderEntry);
hashTable[bucket] = newEntry;
size++;
modCount++;
rehashIfNecessary();
return true;
}
private void rehashIfNecessary() {
if (Hashing.needsResizing(size, hashTable.length, VALUE_SET_LOAD_FACTOR)) {
@SuppressWarnings("unchecked")
ValueEntry[] hashTable = new ValueEntry[this.hashTable.length * 2];
this.hashTable = hashTable;
int mask = hashTable.length - 1;
for (ValueSetLink entry = firstEntry;
entry != this;
entry = entry.getSuccessorInValueSet()) {
ValueEntry valueEntry = (ValueEntry) entry;
int bucket = valueEntry.smearedValueHash & mask;
valueEntry.nextInValueBucket = hashTable[bucket];
hashTable[bucket] = valueEntry;
}
}
}
@CanIgnoreReturnValue
@Override
public boolean remove(@CheckForNull Object o) {
int smearedHash = Hashing.smearedHash(o);
int bucket = smearedHash & mask();
ValueEntry prev = null;
for (ValueEntry entry = hashTable[bucket];
entry != null;
prev = entry, entry = entry.nextInValueBucket) {
if (entry.matchesValue(o, smearedHash)) {
if (prev == null) {
// first entry in the bucket
hashTable[bucket] = entry.nextInValueBucket;
} else {
prev.nextInValueBucket = entry.nextInValueBucket;
}
deleteFromValueSet(entry);
deleteFromMultimap(entry);
size--;
modCount++;
return true;
}
}
return false;
}
@Override
public void clear() {
Arrays.fill(hashTable, null);
size = 0;
for (ValueSetLink entry = firstEntry;
entry != this;
entry = entry.getSuccessorInValueSet()) {
ValueEntry valueEntry = (ValueEntry) entry;
deleteFromMultimap(valueEntry);
}
succeedsInValueSet(this, this);
modCount++;
}
}
@Override
Iterator> entryIterator() {
return new Iterator>() {
ValueEntry nextEntry = multimapHeaderEntry.getSuccessorInMultimap();
@CheckForNull ValueEntry toRemove;
@Override
public boolean hasNext() {
return nextEntry != multimapHeaderEntry;
}
@Override
public Entry next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
ValueEntry result = nextEntry;
toRemove = result;
nextEntry = nextEntry.getSuccessorInMultimap();
return result;
}
@Override
public void remove() {
checkState(toRemove != null, "no calls to next() since the last call to remove()");
LinkedHashMultimap.this.remove(toRemove.getKey(), toRemove.getValue());
toRemove = null;
}
};
}
@Override
Spliterator> entrySpliterator() {
return Spliterators.spliterator(entries(), Spliterator.DISTINCT | Spliterator.ORDERED);
}
@Override
Iterator valueIterator() {
return Maps.valueIterator(entryIterator());
}
@Override
Spliterator valueSpliterator() {
return CollectSpliterators.map(entrySpliterator(), Entry::getValue);
}
@Override
public void clear() {
super.clear();
succeedsInMultimap(multimapHeaderEntry, multimapHeaderEntry);
}
/**
* @serialData the expected values per key, the number of distinct keys, the number of entries,
* and the entries in order
*/
@GwtIncompatible // java.io.ObjectOutputStream
@J2ktIncompatible
private void writeObject(ObjectOutputStream stream) throws IOException {
stream.defaultWriteObject();
stream.writeInt(keySet().size());
for (K key : keySet()) {
stream.writeObject(key);
}
stream.writeInt(size());
for (Entry entry : entries()) {
stream.writeObject(entry.getKey());
stream.writeObject(entry.getValue());
}
}
@GwtIncompatible // java.io.ObjectInputStream
@J2ktIncompatible
private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
stream.defaultReadObject();
multimapHeaderEntry = ValueEntry.newHeader();
succeedsInMultimap(multimapHeaderEntry, multimapHeaderEntry);
valueSetCapacity = DEFAULT_VALUE_SET_CAPACITY;
int distinctKeys = stream.readInt();
Map> map = Platform.newLinkedHashMapWithExpectedSize(12);
for (int i = 0; i < distinctKeys; i++) {
@SuppressWarnings("unchecked")
K key = (K) stream.readObject();
map.put(key, createCollection(key));
}
int entries = stream.readInt();
for (int i = 0; i < entries; i++) {
@SuppressWarnings("unchecked")
K key = (K) stream.readObject();
@SuppressWarnings("unchecked")
V value = (V) stream.readObject();
/*
* requireNonNull is safe for a properly serialized multimap: We've already inserted a
* collection for each key that we expect.
*/
requireNonNull(map.get(key)).add(value);
}
setMap(map);
}
@GwtIncompatible // java serialization not supported
@J2ktIncompatible
private static final long serialVersionUID = 1;
}