1  import java.util.Random;

  2  

  3  /**

  4     This program computes an estimate of pi by simulating dart throws onto a square.

  5  */

  6  public class MonteCarlo

  7  {

  8     public static void main(String[] args)

  9     {  

 10        final int TRIES = 10000;

 11        Random generator = new Random();

 12  

 13        int hits = 0;

 14        for (int i = 1; i <= TRIES; i++)

 15        {  

 16           // Generate two random numbers between -1 and 1

 17  

 18           double r = generator.nextDouble();

 19           double x = -1 + 2 * r; 

 20           r = generator.nextDouble();

 21           double y = -1 + 2 * r;         

 22  

 23           // Check whether the point lies in the unit circle

 24  

 25           if (x * x + y * y <= 1) { hits++; }

 26        }

 27  

 28        /*

 29           The ratio hits / tries is approximately the same as the ratio 

 30           circle area / square area = pi / 4

 31        */        

 32  

 33        double piEstimate = 4.0 * hits / TRIES;

 34        System.out.println("Estimate for pi: " + piEstimate);

 35     }

 36  }