/** pi/4 = 1 - 1/3 + 1/5 - 1/7 + 1/9 - 1/11+...
*/
public class PiCalculator{
    public static void main(String[] args){
        int terms = 200;
        double piEstimate = 0;
        double n = 1;
        for (int i = 0; i < terms; i++){
            if (i%2 == 0) {
                piEstimate = piEstimate + (1 / n); 
            }else{
                piEstimate = piEstimate - (1 / n);                
            }
            n = n + 2;            
        }
        piEstimate = 4 * piEstimate;
        System.out.println("Estimate of pi: " + String.valueOf(piEstimate));
        System.out.println("pi actual: " + String.valueOf(Math.PI));
        System.out.println("pi error: " + String.valueOf(Math.PI - piEstimate));
    }
}