code: //==============================================================================
  //	
  //	Copyright (c) 2016-
  //	Authors:
  //	* Joachim Klein <klein@tcs.inf.tu-dresden.de> (TU Dresden)
  //	
  //------------------------------------------------------------------------------
  //	
  //	This file is part of PRISM.
  //	
  //	PRISM 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.
  //	
  //	PRISM 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 for more details.
  //	
  //	You should have received a copy of the GNU General Public License
  //	along with PRISM; if not, write to the Free Software Foundation,
  //	Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  //	
  //==============================================================================
  
  package common;
  
  /**
   * This class keeps time, returning {@code true} for the method {@code triggered()}
   * when another period of {@code period} milliseconds has elapsed.
   * <br>
   * The time is only checked when {@code triggered} is called, so if there
   * can be long delays between calls to that method, intermediate periods are ignored.
   * <br>
   * This class is thus most helpful for "print some update at least after 5 seconds" style
   * jobs.
   */
  public class PeriodicTimer
  {
  	/** The period */
  	long period;
  	/** The time when the timer was started */
  	long start;
  	/** The time when the last period was detected */
  	long startOfCurrentPeriod;
  
  	/** Constructor, provide the period in milliseconds, e.g., 5000 = 5 seconds */
  	public PeriodicTimer(long periodMillis)
  	{
  		this.period = periodMillis;
  		this.start = -1;
  		this.startOfCurrentPeriod = -1;
  	}
  
  	/** Start the timer */
  	public void start()
  	{
  		start = System.currentTimeMillis();
  		startOfCurrentPeriod = start;
  	}
  
  	/**
  	 * Returns true if at least 'period' milliseconds have
  	 * elapsed since the last time that this method has
  	 * returned {@code true}.
  	 */
  	public boolean triggered()
  	{
  		long now = System.currentTimeMillis();
  		if (now - startOfCurrentPeriod > period) {
  			startOfCurrentPeriod = now;
  			return true;
  		}
  		return false;
  	}
  
  	/** Get the number of milliseconds since {@code start()} was called */
  	public long elapsedMillisTotal()
  	{
  		long now = System.currentTimeMillis();
  		return now - start;
  	}
  
  	/**
  	 * Get the number of milliseconds since {@code triggered()} has returned {@code true}
  	 * the last time
  	 */
  	public long elapsedMillisInThisPeriod()
  	{
  		long now = System.currentTimeMillis();
  		return now - startOfCurrentPeriod;
  	}
  
  }
  