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This is the master POM file for Oracle's Implementation of the JSF 2.2 Specification.
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 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License.  You can
 * obtain a copy of the License at
 * https://glassfish.dev.java.net/public/CDDL+GPL_1_1.html
 * or packager/legal/LICENSE.txt.  See the License for the specific
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package com.sun.faces.util;

import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.logging.Logger;

    /**
     * A concurrent caching mechanism.
     */
public class Cache {

            // Log instance for this class
    private static final Logger LOGGER = FacesLogger.UTIL.getLogger();


        /**
     * Factory interface for creating various cacheable objects.
     */
    public interface Factory {

        V newInstance(final K arg) throws InterruptedException;

    } // END Factory


        private final ConcurrentMap cache =
              new ConcurrentHashMap();
        private final Factory factory;


        // -------------------------------------------------------- Constructors


        /**
         * Constructs this cache using the specified Factory.
         * @param factory
         */
        public Cache(Factory factory) {

            this.factory = factory;

        }


        // ------------------------------------------------------ Public Methods


        /**
         * If a value isn't associated with the specified key, a new
         * {@link java.util.concurrent.Callable} will be created wrapping the Factory
         * specified via the constructor and passed to a {@link java.util.concurrent.FutureTask}.  This task
         * will be passed to the backing ConcurrentMap.  When {@link java.util.concurrent.FutureTask#get()}
         * is invoked, the Factory will return the new Value which will be cached
         * by the {@link java.util.concurrent.FutureTask}.
         *
         * @param key the key the value is associated with
         * @return the value for the specified key, if any
         */
        public V get(final K key) {
          V result = cache.get(key);
          
          if (result == null)
          {
            try
            {
              result = factory.newInstance(key);
            }
            catch (InterruptedException ie)
            {
              // will never happen. Just for testing
              throw new RuntimeException(ie);
            }
            
            // put could be used instead if it didn't matter whether we replaced
            // an existing entry
            V oldResult = cache.putIfAbsent(key, result);
            
            if (oldResult != null)
              result = oldResult;
          }
          
          return result;
        }

        public V remove(final K key) {
          return cache.remove(key);

    }

    } // END Cache