core/runtime/src/main/java/org/apache/polygene/runtime/composite/SynchronizedCompositeMethodInstancePool.java

/*
 *  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.polygene.runtime.composite;

/**
 * Method instance pool that keeps a linked list. Uses synchronization
 * to ensure that instances are acquired and returned in a thread-safe
 * manner.
 */
public final class SynchronizedCompositeMethodInstancePool
    implements InstancePool<CompositeMethodInstance>
{
    private CompositeMethodInstance first = null;

    @Override
    public synchronized CompositeMethodInstance obtainInstance()
    {
        CompositeMethodInstance instance = first;
        if( instance != null )
        {
            first = instance.getNext();
        }
        return instance;
    }

    @Override
    public synchronized void releaseInstance( CompositeMethodInstance instance )
    {
        instance.setNext( first );
        first = instance;
    }
}