    001    // Copyright 2006, 2007 The Apache Software Foundation
    002    //
    003    // Licensed under the Apache License, Version 2.0 (the "License");
    004    // you may not use this file except in compliance with the License.
    005    // You may obtain a copy of the License at
    006    //
    007    //     http://www.apache.org/licenses/LICENSE-2.0
    008    //
    009    // Unless required by applicable law or agreed to in writing, software
    010    // distributed under the License is distributed on an "AS IS" BASIS,
    011    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    012    // See the License for the specific language governing permissions and
    013    // limitations under the License.
    014
    015    package org.apache.tapestry5.internal.util;
    016
    017    import java.util.concurrent.atomic.AtomicReference;
    018
    019    /**
    020     * An object that holds some type of other object. This is useful for communicating information from an inner class
    021     * (used as a closure) to the containing method. This is similar to {@link AtomicReference}, except that it is simpler
    022     * but <strong>not</strong> thread safe.
    023     *
    024     * @param <T>
    025     */
    026    public class Holder<T>
    027    {
    028        private T held;
    029
    030        public void put(T object)
    031        {
    032            held = object;
    033        }
    034
    035        public T get()
    036        {
    037            return held;
    038        }
    039
    040        public boolean hasValue()
    041        {
    042            return held != null;
    043        }
    044
    045        public static <T> Holder<T> create()
    046        {
    047            return new Holder<T>();
    048        }
    049    }