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The ActiveMQ Message Broker implementation

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/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.activemq.memory;

public class CacheEntry {

    public final Object key;
    public final Object value;

    public CacheEntry next;
    public CacheEntry previous;
    public CacheEntryList owner;

    public CacheEntry(Object key, Object value) {
        this.key = key;
        this.value = value;
    }

    /**
     * @return false if you are trying to remove the tail pointer.
     */
    public boolean remove() {

        // Cannot remove if this is a tail pointer.
        // Or not linked.
        if (owner == null || this.key == null || this.next == null) {
            return false;
        }

        synchronized (owner.tail) {
            this.next.previous = this.previous;
            this.previous.next = this.next;
            this.owner = null;
            this.next = null;
            this.previous = null;
        }

        return true;
    }
}