CS302 Exam 2 Spring 2013 Reference Solution

Part I: Write a complete program

import java.util.Scanner;
public class EstimatePI {
    public static void main(String[] args) {
        Scanner scnr = new Scanner(System.in);
        System.out.print("Enter the number of darts: ");
        if ( !scnr.hasNextInt() ) errorMsg();
        int darts = scnr.nextInt(); // random throws per trial
        if ( darts < 1 ) errorMsg();

        // The simulation
        int side = 2; // the length of the side of a rectangle
        int radius = side/2; // the radius of the circle

        int inCircle = 0;
        for ( int p=0; p < darts; p++ ) {
            double x = Math.random()*side;
            double y = Math.random()*side;
            double d = Math.sqrt(Math.pow(x-radius,2)+
                Math.pow(y-radius,2));
            if ( d <= radius )
                inCircle++;
        }
        double pi_est = 4.0*(inCircle/(double)darts);
        System.out.print("Darts IN="+inCircle);
        System.out.println(" PI="+pi_est);
    }

    private static void errorMsg() {
        System.out.println("Must [be|enter] a positive integer!");
        System.exit(-1);
    }
}