org.jboss.weld.util.LazyValueHolder Maven / Gradle / Ivy
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* JBoss, Home of Professional Open Source
* Copyright 2008, 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;
/**
* Represents a lazily computed value.
*
* @author Stuart Douglas
*/
public abstract class LazyValueHolder implements ValueHolder {
public static Function> forValue() {
return new Function>() {
@Override
public ValueHolder apply(final V value) {
return new LazyValueHolder() {
@Override
protected V computeValue() {
return value;
}
};
}
};
}
private transient volatile T value;
public T get() {
T valueCopy = value;
if (valueCopy != null) {
return valueCopy;
}
synchronized (this) {
if (value == null) {
value = computeValue();
}
return value;
}
}
@Override
public T getIfPresent() {
return value;
}
public void clear() {
synchronized (this) {
value = null;
}
}
protected abstract T computeValue();
/**
* {@link LazyValueHolder} that implements {@link java.io.Serializable}.
*
* @author Jozef Hartinger
*
* @param the lazily-computed type
*/
public abstract static class Serializable extends LazyValueHolder implements java.io.Serializable {
private static final long serialVersionUID = 1L;
}
}