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/*
* Copyright (C) 2002-2022 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 ObjectSets {
private ObjectSets() {}
/** 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 ObjectCollections.EmptyCollection implements ObjectSet , 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 ObjectSet UNMODIFIABLE_EMPTY_SET = ObjectSets.unmodifiable(new ObjectArraySet(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 ObjectSet 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 AbstractObjectSet 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 java.util.Objects.equals(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 ObjectSet singleton(final K element) {
return new Singleton <>(element);
}
/** A synchronized wrapper class for sets. */
public static class SynchronizedSet extends ObjectCollections.SynchronizedCollection implements ObjectSet , java.io.Serializable {
private static final long serialVersionUID = -7046029254386353129L;
protected SynchronizedSet(final ObjectSet s, final Object sync) {
super(s, sync);
}
protected SynchronizedSet(final ObjectSet 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 ObjectSet synchronize(final ObjectSet 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 ObjectSet synchronize(final ObjectSet s, final Object sync) { return new SynchronizedSet <>(s, sync); }
/** An unmodifiable wrapper class for sets. */
public static class UnmodifiableSet extends ObjectCollections.UnmodifiableCollection implements ObjectSet , java.io.Serializable {
private static final long serialVersionUID = -7046029254386353129L;
protected UnmodifiableSet(final ObjectSet 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 ObjectSet unmodifiable(final ObjectSet s) { return new UnmodifiableSet <>(s); }
}