org.jboss.weld.util.WeakLazyValueHolder Maven / Gradle / Ivy
/*
* JBoss, Home of Professional Open Source
* Copyright 2014, Red Hat, Inc., and individual contributors
* by the @authors tag. See the copyright.txt in the distribution for a
* full listing of individual contributors.
*
* 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 org.jboss.weld.util;
import java.lang.ref.WeakReference;
/**
* {@link LazyValueHolder} that uses {@link WeakReference}.
*
* @author Jozef Hartinger
*
* @param
*/
public abstract class WeakLazyValueHolder implements ValueHolder {
public static Function> forValue() {
return new Function>() {
@Override
public ValueHolder apply(final V value) {
return new WeakLazyValueHolder() {
@Override
protected V computeValue() {
return value;
}
};
}
};
}
private volatile WeakReference reference;
public T get() {
WeakReference reference = this.reference;
T value = null;
if (reference != null) {
value = reference.get();
}
if (value != null) {
return value;
}
synchronized (this) {
if (this.reference == reference) {
T newValue = computeValue();
this.reference = new WeakReference(newValue);
}
return this.reference.get();
}
}
@Override
public T getIfPresent() {
WeakReference reference = this.reference;
if (reference != null) {
return reference.get();
}
return null;
}
public void clear() {
synchronized (this) {
reference = null;
}
}
protected abstract T computeValue();
}