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/*
* Copyright (C) 2023 Parisi Alessandro - [email protected]
* This file is part of MaterialFX (https://github.com/palexdev/MaterialFX)
*
* MaterialFX is free software: you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
* as published by the Free Software Foundation; either version 3 of the License,
* or (at your option) any later version.
*
* MaterialFX is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
* See the GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with MaterialFX. If not, see extends HashSet {
//================================================================================
// Properties
//================================================================================
private final Set> set = new HashSet<>();
// Helps detect GCed values
private final ReferenceQueue queue = new ReferenceQueue<>();
//================================================================================
// Constructors
//================================================================================
public WeakHashSet() {
}
public WeakHashSet(Collection c) {
super(c);
}
public WeakHashSet(int initialCapacity, float loadFactor) {
super(initialCapacity, loadFactor);
}
public WeakHashSet(int initialCapacity) {
super(initialCapacity);
}
//================================================================================
// Methods
//================================================================================
/**
* Adds the specified element to this set if it is not already
* present.
*
* @param t element to be added to this set.
* @return `true` if the set did not already contain the specified
* element.
*/
@Override
public boolean add(T t) {
processQueue();
return set.add(WeakElement.of(t, queue));
}
@Override
public boolean addAll(Collection c) {
for (T t : c) {
if (!add(t)) {
return false;
}
}
return true;
}
@Override
public boolean retainAll(Collection c) {
Set itemsToRemove = new HashSet<>(c.size());
for (T t : this) {
if (!c.contains(t)) {
itemsToRemove.add(t);
}
}
if (itemsToRemove.isEmpty()) return false;
for (T t : itemsToRemove) {
remove(t);
}
return true;
}
/**
* Removes the given element from this set if it is present.
*
* @param o object to be removed from this set, if present.
* @return `true` if the set contained the specified element.
*/
@Override
public boolean remove(Object o) {
boolean ret = set.remove(WeakElement.of(o));
processQueue();
return ret;
}
@Override
public boolean removeAll(Collection c) {
boolean changed = false;
for (Object o : c) {
if (remove(o)) changed = true;
}
return changed;
}
@Override
public void clear() {
}
/**
* Returns `true` if this set contains the specified element.
*
* @param o element whose presence in this set is to be tested.
* @return `true` if this set contains the specified element.
*/
@Override
public boolean contains(Object o) {
return set.contains(WeakElement.of(o));
}
@Override
public boolean containsAll(Collection c) {
for (Object o : c) {
if (!contains(o)) {
return false;
}
}
return true;
}
@Override
public int size() {
return set.size();
}
@Override
public boolean isEmpty() {
return set.isEmpty();
}
/**
* Returns an iterator over the elements in this set. The elements
* are returned in no particular order.
*
* @return an Iterator over the elements in this set.
*/
@Override
public Iterator iterator() {
// Remove GCed elements
processQueue();
Iterator> it = set.iterator();
return new Iterator<>() {
@Override
public boolean hasNext() {
return it.hasNext();
}
@Override
public T next() {
return it.next().get();
}
@Override
public void remove() {
it.remove();
}
};
}
/**
* Removes all GCed values from the delegate Set.
* Since we don't know how much the ReferenceQueue.poll() operation
* costs, we should call it only in methods that change the Set, like add or remove.
*/
protected void processQueue() {
WeakElement e;
while (true) {
e = (WeakElement) queue.poll();
if (e == null) break;
set.remove(e);
}
}
//================================================================================
// Internal Classes
//================================================================================
/**
* A {@code WeakHasSet} stores objects of class WeakElement.
* A {@code WeakElement} wraps the element that should be stored in the {@code WeakHashSet}.
* {@code WeakElement} inherits from {@link WeakReference}.
* It redefines equals and hashCode which delegate to the corresponding methods
* of the wrapped element.
*/
protected static class WeakElement extends WeakReference {
private final int hash;
public WeakElement(T t) {
super(t);
this.hash = (t != null) ? t.hashCode() : 0;
}
public WeakElement(T t, ReferenceQueue q) {
super(t, q);
this.hash = (t != null) ? t.hashCode() : 0;
}
public static WeakElement of(T t) {
return new WeakElement<>(t);
}
public static WeakElement of(T t, ReferenceQueue q) {
return new WeakElement<>(t, q);
}
/**
* A {@code WeakElement} is equal to another {@code WeakElement} if they both refer to objects
* that are, in turn, equal according to their own equals methods
*/
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
T t = get();
Object oT = ((WeakElement) o).get();
if (t == oT) return true;
return (t == null || oT == null) ? false : t.equals(oT);
}
@Override
public int hashCode() {
return hash;
}
}
}