main.java

public class main {
    public static void main(String[] args) {
    
        // Get the number of rounds.
        String strRounds = System.getenv("rounds");
        if (strRounds == null) {
            System.out.printf("*** The 'rounds' environment variable is not set\n");
            System.exit(1);
        }
        long rounds = -1;
        try {
            rounds = Long.parseLong(strRounds);
        } catch (NumberFormatException e) {
            System.out.printf("*** The 'rounds' environment variable must be an integer, saw: %s\n", strRounds);
            System.exit(1);
        }
        
        double sum = 0.0;
        double flip = -1.0;
        long tStart, tStop;
        double pi;
        long ix;
        
        // Prime the caches.
        for (ix = 1; ix <= rounds; ix++) {
            flip *= -1.0;
            sum += flip / (double) (ix + ix - 1);
        }
        sum = 0.0;
        flip = -1.0;

        // Timed test.
        tStart = System.nanoTime();
        for (ix = 1; ix <= rounds; ix++) {
            flip *= -1.0;
            sum += flip / (double) (ix + ix - 1);
        }
        pi = sum * 4.0;
        tStop = System.nanoTime();

        // Report.
        double tDeltaSecs = (tStop - tStart) / 1e9;
        System.out.printf("Java,%d,%.3f,%.40f\n", rounds, tDeltaSecs, pi); 
    }
}