IntegerCache.java

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/* *********************************************************************** *
 * project: org.matsim.*
 * IntegerCache.java
 *                                                                         *
 * *********************************************************************** *
 *                                                                         *
 * copyright       : (C) 2007 by the members listed in the COPYING,        *
 *                   LICENSE and WARRANTY file.                            *
 * email           : info at matsim dot org                                *
 *                                                                         *
 * *********************************************************************** *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *   See also COPYING, LICENSE and WARRANTY file                           *
 *                                                                         *
 * *********************************************************************** */

package org.matsim.core.utils.misc;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

public class IntegerCache {
    // yyyy not sure what this class is doing.  as long as MIN_VALUE=0 (as I am finding it), it just seems to receive an
    // Integer, and return an Integer of the same value.  Maybe there was historically a situation where this did not start 
    // at 0, and then one wanted to get rid of the (un)boxing overhead? kai, jan'16
    
    private final static Logger log = LogManager.getLogger(IntegerCache.class);
        
    
    private static final int MIN_VALUE = 0;
    private static final int MAX_VALUE = 8192;
    
    private static boolean initialized = false;
    private static Integer [] cache;

    public static Integer getInteger(final int i) {
        
        if (!initialized) {
            init();
        }

        if ( i < MAX_VALUE && i >= MIN_VALUE) {
            return cache[i + MIN_VALUE];
        }
        
        return Integer.valueOf(i);
    }
    
    synchronized private static void init() {
        if (initialized) {
            log.warn("IntegerCache has already been initialized.");
            return;
        }
        
        log.info("Initializing IntegerCache ...");
        cache = new Integer [MAX_VALUE - MIN_VALUE];
        for (int i = 0; i < (MAX_VALUE - MIN_VALUE); i++) {
            cache[i] = Integer.valueOf(i - MIN_VALUE);
        }
        log.info("done.");
        initialized = true;
    }
    
}