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/*
* Copyright (C) 2002-2023 Sebastiano Vigna
*
* 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 it.unimi.dsi.fastutil.objects;
import java.util.Collection;
import java.util.Set;
import java.util.function.Consumer;
/**
* A class providing static methods and objects that do useful things with type-specific sets.
*
* @see java.util.Collections
*/
public final class ReferenceSets {
private ReferenceSets() {
}
/** The maximum size to choose ArraySet over OpenHashSet for utilites that automatically choose. */
static final int ARRAY_SET_CUTOFF = 4;
/**
* An immutable class representing the empty set and implementing a type-specific set interface.
*
*
* This class may be useful to implement your own in case you subclass a type-specific set.
*/
public static class EmptySet extends ReferenceCollections.EmptyCollection implements ReferenceSet, java.io.Serializable, Cloneable {
private static final long serialVersionUID = -7046029254386353129L;
protected EmptySet() {
}
@Override
public boolean remove(Object ok) {
throw new UnsupportedOperationException();
}
@Override
public Object clone() {
return EMPTY_SET;
}
@Override
@SuppressWarnings("rawtypes")
public boolean equals(final Object o) {
return o instanceof Set && ((Set)o).isEmpty();
}
private Object readResolve() {
return EMPTY_SET;
}
}
/**
* An empty set (immutable). It is serializable and cloneable.
*/
@SuppressWarnings("rawtypes")
public static final EmptySet EMPTY_SET = new EmptySet();
// Used by Sets.of() instead of SETS.EMPTY_SET to make a dimorphic call site.
// See https://github.com/vigna/fastutil/issues/183
@SuppressWarnings({ "unchecked", "rawtypes" })
static final ReferenceSet UNMODIFIABLE_EMPTY_SET = ReferenceSets.unmodifiable(new ReferenceArraySet(ObjectArrays.EMPTY_ARRAY));
/**
* Returns an empty set (immutable). It is serializable and cloneable.
*
*
* This method provides a typesafe access to {@link #EMPTY_SET}.
*
* @return an empty set (immutable).
*/
@SuppressWarnings("unchecked")
public static ReferenceSet emptySet() {
return EMPTY_SET;
}
/**
* An immutable class representing a type-specific singleton set.
*
*
* This class may be useful to implement your own in case you subclass a type-specific set.
*/
public static class Singleton extends AbstractReferenceSet implements java.io.Serializable, Cloneable {
private static final long serialVersionUID = -7046029254386353129L;
protected final K element;
protected Singleton(final K element) {
this.element = element;
}
@Override
public boolean contains(final Object k) {
return ((k) == (element));
}
@Override
public boolean remove(final Object k) {
throw new UnsupportedOperationException();
}
@Override
public ObjectListIterator iterator() {
return ObjectIterators.singleton(element);
}
@Override
public ObjectSpliterator spliterator() {
return ObjectSpliterators.singleton(element);
}
@Override
public int size() {
return 1;
}
@Override
public Object[] toArray() {
return new Object[] { element };
}
@Override
public void forEach(final Consumer action) {
action.accept((element));
}
@Override
public boolean addAll(final Collection c) {
throw new UnsupportedOperationException();
}
@Override
public boolean removeAll(final Collection c) {
throw new UnsupportedOperationException();
}
@Override
public boolean retainAll(final Collection c) {
throw new UnsupportedOperationException();
}
@Override
public boolean removeIf(final java.util.function.Predicate filter) {
throw new UnsupportedOperationException();
}
@Override
public Object clone() {
return this;
}
}
/**
* Returns a type-specific immutable set containing only the specified element. The returned set is
* serializable and cloneable.
*
* @param element the only element of the returned set.
* @return a type-specific immutable set containing just {@code element}.
*/
public static ReferenceSet singleton(final K element) {
return new Singleton<>(element);
}
/** A synchronized wrapper class for sets. */
public static class SynchronizedSet extends ReferenceCollections.SynchronizedCollection implements ReferenceSet, java.io.Serializable {
private static final long serialVersionUID = -7046029254386353129L;
protected SynchronizedSet(final ReferenceSet s, final Object sync) {
super(s, sync);
}
protected SynchronizedSet(final ReferenceSet s) {
super(s);
}
@Override
public boolean remove(final Object k) {
synchronized (sync) {
return collection.remove(k);
}
}
}
/**
* Returns a synchronized type-specific set backed by the given type-specific set.
*
* @param s the set to be wrapped in a synchronized set.
* @return a synchronized view of the specified set.
* @see java.util.Collections#synchronizedSet(Set)
*/
public static ReferenceSet synchronize(final ReferenceSet s) {
return new SynchronizedSet<>(s);
}
/**
* Returns a synchronized type-specific set backed by the given type-specific set, using an assigned
* object to synchronize.
*
* @param s the set to be wrapped in a synchronized set.
* @param sync an object that will be used to synchronize the access to the set.
* @return a synchronized view of the specified set.
* @see java.util.Collections#synchronizedSet(Set)
*/
public static ReferenceSet synchronize(final ReferenceSet s, final Object sync) {
return new SynchronizedSet<>(s, sync);
}
/** An unmodifiable wrapper class for sets. */
public static class UnmodifiableSet extends ReferenceCollections.UnmodifiableCollection implements ReferenceSet, java.io.Serializable {
private static final long serialVersionUID = -7046029254386353129L;
protected UnmodifiableSet(final ReferenceSet s) {
super(s);
}
@Override
public boolean remove(final Object k) {
throw new UnsupportedOperationException();
}
@Override
public boolean equals(final Object o) {
if (o == this) return true;
return collection.equals(o);
}
@Override
public int hashCode() {
return collection.hashCode();
}
}
/**
* Returns an unmodifiable type-specific set backed by the given type-specific set.
*
* @param s the set to be wrapped in an unmodifiable set.
* @return an unmodifiable view of the specified set.
* @see java.util.Collections#unmodifiableSet(Set)
*/
public static ReferenceSet unmodifiable(final ReferenceSet s) {
return new UnmodifiableSet<>(s);
}
}