The class to generate random number obey exponential distribution

ExponentialDistribution.java

package simulation.util;

import java.text.DecimalFormat;

/*
 * The numbers generated by java Random is using Uniform Distribution. 
 * But recently, when I work on Timed-Petri net, it is better to use Exponential Distribution.
 * Thus, I write a class which is like a exponential calculator.
 * 
 * INPUT: lamda
 * OUTPUT: random number based on Exponential Distribution
 */

public class ExponentialDistribution {

	public double getExponential(double time) {
		double x, z;
		double lamda = 1 / time;
		z = Math.random();
		x = (-(1 / lamda) * Math.log(z));
		x = format(x);
		return x;
	}

	public double format(double x) {
		return Double.parseDouble(new DecimalFormat("##.##").format(x));
	}

}