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Java example source code file (RepositoryIdCache.java)

This example Java source code file (RepositoryIdCache.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

hashtable, max_cache_size, repositoryid, repositoryidcache, repositoryidpool, stack, util

The RepositoryIdCache.java Java example source code

/*
 * Copyright (c) 1998, 2002, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
/*
 * Licensed Materials - Property of IBM
 * RMI-IIOP v1.0
 * Copyright IBM Corp. 1998 1999  All Rights Reserved
 *
 */

package com.sun.corba.se.impl.util;

import java.util.Stack;
import java.util.Hashtable;
import java.util.EmptyStackException;
import java.util.Enumeration;

// Really limited pool - in this case just creating several at a time...
class RepositoryIdPool extends Stack {

    private static int MAX_CACHE_SIZE = 4;
    private RepositoryIdCache cache;

    public final synchronized RepositoryId popId() {

        try {
            return (RepositoryId)super.pop();
        }
        catch(EmptyStackException e) {
            increasePool(5);
            return (RepositoryId)super.pop();
        }

    }

    // Pool management
    final void increasePool(int size) {
        //if (cache.size() <= MAX_CACHE_SIZE)
        for (int i = size; i > 0; i--)
            push(new RepositoryId());
        /*
          // _REVISIT_ This will not work w/out either thread tracing or weak references.  I am
          // betting that thread tracing almost completely negates benefit of reuse.  Until either
          // 1.2 only inclusion or proof to the contrary, I'll leave it this way...
          else {
          int numToReclaim = cache.size() / 2;
          Enumeration keys = cache.keys();
          Enumeration elements = cache.elements();
          for (int i = numToReclaim; i > 0; i--) {
          Object key = keys.nextElement();
          Object element = elements.nextElement();

          push(element);
          cache.remove(key);
          }
          }
        */
    }

    final void setCaches(RepositoryIdCache cache) {
        this.cache = cache;
    }

}

public class RepositoryIdCache extends Hashtable {

    private RepositoryIdPool pool = new RepositoryIdPool();

    public RepositoryIdCache() {
        pool.setCaches(this);
    }

    public final synchronized RepositoryId getId(String key) {
        RepositoryId repId = (RepositoryId)super.get(key);

        if (repId != null)
            return repId;
        else {
            //repId = pool.popId().init(key);
            repId = new RepositoryId(key);
            put(key, repId);
            return repId;
        }

    }
}

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