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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 {
    private volatile T value;

    public T get() {
        T valueCopy = value;
        if (valueCopy != null) {
            return valueCopy;
        }
        synchronized (this) {
            if (value == null) {
                value = computeValue();
            }
            return value;
        }
    }

    public void clear() {
        synchronized (this) {
            value = null;
        }
    }

    protected abstract T computeValue();
}