SimpleRandomWalk.java

/*
 * Created on Feb 7, 2004
 *
 * A source of numbers in a bounded random walk.
 */
package org.nees.rbnb;

import java.util.Random;

public class SimpleRandomWalk {
    
    private static final double MIN_VALUE = -10.0;
    private static final double MAX_VALUE = 10.0;
    private static final boolean WRAP = true;
    
    private double minValue;
    private double maxValue;
    private double current;
    private boolean wrap;
    
    private Random source;
    
    public SimpleRandomWalk()
    {
        init(MIN_VALUE,MAX_VALUE,WRAP);
    }
    
    public SimpleRandomWalk(double min, double max, boolean wrap)
    {
        init(min,max,wrap);
    }
    
    private void init(double min, double max, boolean flag) {
        minValue = min;
        maxValue = max;
        current = (min + max)/2.0;
        wrap = flag;
        source = new Random();
    }

    public double next()
    {
        double step = (2.0 * source.nextDouble()) - 1.0;
        if ((current+step) > maxValue)
        {
            if (wrap) current = minValue + ((current+step)-maxValue);
            else // reflect
                current = maxValue + (maxValue-(current+step));
        }
        else if ((current+step) < minValue)
        {
            if (wrap) current = maxValue + ((current+step)-minValue);
            else // reflect
                current = minValue + (minValue - (current+step));
        }
        else current += step;
        
        return current;
    }
    
    public static void main (String[] args)
    {
        SimpleRandomWalk w = new SimpleRandomWalk();
        
        for (int i = 0; i < 10000; i++)
        {
            System.out.println(i + ": " + w.next());
        }
    }
}

---