Java class that performs a fixed rate simulation.

Simulation.java

/*
 * Copyright (c) 2012 Michael Nischt
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 * Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
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 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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/**
 * Class that performs a fixed rate simulation.
 *
 * @author Michael Nischt
 */
public final class Simulation {

    /**
     * Callback interface which is called once for every simulation step at the specified intervall
     */
    public interface Updater {
        void update(double dT);
    }
    
    private static final double SIM_RATE = 1.0/60.0;
    
    private final Updater updater;
    private final double stepDuration;
    
    private long lastTime;
    private double remainingTime;

    /**
     * Creates a new simulation routine which calls the updater with a frequency of 60Hz.
     * @param updater the simulation callback interface
     */
    public Simulation(Updater updater) {
        this(updater, SIM_RATE);
    }
    /**
     * Creates a new simulation routine which calls the updater with a frequency of 60Hz.
     * @param updater the simulation callback interface
     * @param stepDuration the duration of a single simulation step
     */
    public Simulation(Updater updater, double stepDuration) {
         if(updater == null) {
             throw new NullPointerException();
         }
         if(stepDuration <= 0) {
             throw new IllegalArgumentException();
         }
         this.updater = updater;
         this.stepDuration = stepDuration;
    }
    
    /**
     * Update fuction thats calls the callback as many times as the simulation inverval fits into passed time 
     * since the last call.
     * If the passed time is greated than 100 times the interval, no simulation will take place.
     */
    public void update() {        
        long now = System.nanoTime();
                
        double deltaTime = (now - lastTime) / 1e09 + remainingTime;
        if(deltaTime > 100*stepDuration) {
            // skip pause
            lastTime = now;
            remainingTime = 0;
            return;
        }
        
        while(deltaTime >= stepDuration) {
            // fixed rate update
            updater.update(stepDuration);
            deltaTime -= stepDuration;
        }
                
        lastTime = now;
        remainingTime = deltaTime;
    }
}