// LoopsMonteCarlo Example
// Module: montecarlo
// Estimate the value of pi by generating
// random pairs (x, y) where x and y in [0,1.0).
// The probability of (x, y) lying in the circle
// with center (0,5, 0,5) and radius 1 is pi/4.

import java.util.Random;
public class Main {

    // Define number of rolls.
    public final static int NUM_DART_THROWS = 10000000;

    public static void main(String[] args) {

        // Define random number generator
        Random rand = new Random( );

        // Define variables.
        double x, y, dist;
        int numSuccesses = 0;

        // Throw darts. Count as success only throws
        // in the circle with center (0,5, 0,5) and radius 1.
        for(int i = 1; i <= NUM_DART_THROWS; i++) {
            x = rand.nextDouble( );
            y = rand.nextDouble( );
            dist = Math.sqrt(Math.pow(x - 0.5, 2.0) +
                    Math.pow(y - 0.5, 2.0));
            if (dist <= 0.5) {
                numSuccesses++;
            }
        }

        // Print result
        System.out.print("Estimate for pi: ");
        System.out.println(4.0 * ((double) numSuccesses) /
                NUM_DART_THROWS);
    }
}