net.sf.ehcache.store.MemoryStoreEvictionPolicy.java Source code

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Here is the source code for net.sf.ehcache.store.MemoryStoreEvictionPolicy.java

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/**
 *  Copyright 2003-2007 Luck Consulting Pty Ltd
 *
 *  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 net.sf.ehcache.store;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.io.Serializable;

/**
 * A typesafe enumeration of eviction policies.
 * The policy used to evict elements from the {@link net.sf.ehcache.store.MemoryStore}.
 * This can be one of:                                                                
 * <ol>
 * <li>LRU - least recently used
 * <li>LFU - least frequently used
 * <li>FIFO - first in first out, the oldest element by creation time
 * </ol>
 * The default value is LRU
 *
 * @author <a href="mailto:gluck@thoughtworks.com">Greg Luck</a>
 * @version $Id: MemoryStoreEvictionPolicy.java 519 2007-07-27 07:11:45Z gregluck $
 * @since 1.2
 */
public final class MemoryStoreEvictionPolicy implements Serializable {

    /**
     * LRU - least recently used.
     */
    public static final MemoryStoreEvictionPolicy LRU = new MemoryStoreEvictionPolicy("LRU");

    /**
     * LFU - least frequently used.
     */

    public static final MemoryStoreEvictionPolicy LFU = new MemoryStoreEvictionPolicy("LFU");

    /**
     * FIFO - first in first out, the oldest element by creation time.
     */
    public static final MemoryStoreEvictionPolicy FIFO = new MemoryStoreEvictionPolicy("FIFO");

    private static final Log LOG = LogFactory.getLog(MemoryStoreEvictionPolicy.class.getName());

    private final String myName;

    /**
     * This class should not be subclassed or have instances created.
     * @param policy
     */
    private MemoryStoreEvictionPolicy(String policy) {
        myName = policy;
    }

    /**
     * @return a String representation of the policy
     */
    public String toString() {
        return myName;
    }

    /**
     * Converts a string representation of the policy into a policy.
     *
     * @param policy either LRU, LFU or FIFO
     * @return one of the static instances
     */
    public static MemoryStoreEvictionPolicy fromString(String policy) {
        if (policy != null) {
            if (policy.equalsIgnoreCase("LRU")) {
                return LRU;
            } else if (policy.equalsIgnoreCase("LFU")) {
                return LFU;
            } else if (policy.equalsIgnoreCase("FIFO")) {
                return FIFO;
            }
        }

        if (LOG.isWarnEnabled()) {
            LOG.warn("The memoryStoreEvictionPolicy of " + policy + " cannot be resolved. The policy will be"
                    + " set to LRU");
        }
        return LRU;
    }
}