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Interim replacement for JSR 77 Stats and Statistics
There is a newer version: 8.0.0-JDK17-M9
/*
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 *
 * Copyright (c) 1997-2011 Oracle and/or its affiliates. All rights reserved.
 *
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 * 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
 * language governing permissions and limitations under the License.
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package com.sun.enterprise.admin.monitor.stats;
import org.glassfish.j2ee.statistics.TimeStatistic;
import org.glassfish.j2ee.statistics.Statistic;


/** An implementation of {@link MutableTimeStatistic} that eases the various
 * statistical calculations.
 * @author  Kedar Mhaswade
 * @since S1AS8.0
 * @version $Revision: 1.2 $
 */
public class MutableTimeStatisticImpl implements TimeStatistic, MutableTimeStatistic {
	
	private final TimeStatistic initial;
	private long methodCount;
	private long min;
	private long max;
	private long total; //possibility of an overflow?
	private long lastSampleTime;
	/**
	 * Constructs an instance of this class from its immutable equivalent. Note that there are
	 * some constraints on the parameter passed:
	 * 
	 *   The maxTime, minTime and totTime of param must be same 
	 * 
	 * @param       instance of (immutable) {@link TimeStatistic}
	 */
	public MutableTimeStatisticImpl(TimeStatistic initial) {
		this.initial        = initial;
		methodCount         = initial.getCount();
		min    = initial.getMinTime();
		max    = initial.getMaxTime();
		total  = initial.getTotalTime();
		final boolean minMax = min == max;
		final boolean minTot = min == total;
		if (! (minMax && minTot))
			throw new IllegalArgumentException("Invalid initial values: " + min + ", " + max + ", " + total);
		lastSampleTime = initial.getLastSampleTime();
	}
	
	/**
	 * Increments the count of operation execution by 1 and also increases the time
	 * consumed. A successful execution of method will have all the data updated as:
	 * 
	 *  method count ++ 
	 *  max time, min time and total time are accordingly adjusted 
	 * 
	 * @param       current     long indicating time in whatever unit this statistic is calculated
	 */
	public void incrementCount(long current) {
        if (methodCount == 0) {
            total = max = min = current;
        } else {
            total += current;
            max = current >= max ? current : max;
            min = current >= min ? min : current;
        }
		methodCount++;
		lastSampleTime = System.currentTimeMillis();
	}
	
	/**
	 * Resets the Statistic. Calling this method has following effect:
	 * 
	 *  Initial state of this Statistic is restored as far as Count, Minimum/Maximum
	 * and Total time of execution is considered. 
	 * 
	 */
	public void reset() {
		methodCount         = initial.getCount();
		min                 = initial.getMinTime();
		max                 = initial.getMaxTime();
		total               = initial.getTotalTime();
		lastSampleTime	    = initial.getLastSampleTime();
	}
	
	/**
	 * This method is the essence of this class. Returns the unmodifiable view
	 * of this instance.
	 * @return an instance of {@link TimeStatistic}
	 */
	public Statistic unmodifiableView() {
		return ( new TimeStatisticImpl(
		this.methodCount,
		this.max,
		this.min,
		this.total,
		initial.getName(),
		initial.getUnit(),
		initial.getDescription(),
		initial.getStartTime(),
		this.lastSampleTime )
		);
	}
	
	public Statistic modifiableView() {
		return ( this );
	}
	
	public long getCount() {
		return ( this.methodCount);
	}
	
	public String getDescription() {
		return ( initial.getDescription() );
	}
	
	public long getLastSampleTime() {
		return ( this.lastSampleTime );
	}
	
	public long getMaxTime() {
		return ( this.max );
	}
	
	public long getMinTime() {
		return ( this.min );
	}
	
	public String getName() {
		return ( initial.getName() );
	}
	
	public long getStartTime() {
		return ( initial.getStartTime() );
	}
	
	public long getTotalTime() {
		return ( this.total );
	}
	
	public String getUnit() {
		return ( initial.getUnit() );
	}
    /* hack: bug 5045413 */
    public void setDescription (final String s) {
        try {
            ((StatisticImpl)this.initial).setDescription(s);
        }
        catch(final Exception e) {
        }
    }
}