My simple Java pi calculator always seems to give infinity?

Question

I am coding this simple pi calculator for my Java class as a part of us learning about basic loops and it seems like everything is OK except the values printed for pi is infinity when it should be 3.14...something according to the number of iterations. I read that this could be maybe related to a double variable dividing by 0 and it's giving a weird infinity output instead of a normal Java runtime exception?

Here's my code:

package lab05;
public class Lab05 {
    public static void main(String[] args) {
        // Variable declarations
        double pie = 3;
        double savepie = 0;
        double term = 0;
        double savei = 0;
        double sign = 1;
        boolean isRangeFound = false;
        int i;
        // For loop
        for (i=0; i <= 1000;) { // Only up to 1000 iterations before loop must end.
            term = (sign * 4) / ((2*i) * (2*i+1) * (2*i+2));
            pie = pie + term;
            sign = (-1 * sign);
            if (isRangeFound==false && (pie >=3.14159265 & pie < 3.14159266)) {
                savepie = pie;
                savei = i;
                isRangeFound = true;
            }
            if (i == 200||i == 500||i == 1000) {
                System.out.print("The value of \u03C0 is: ");
                System.out.printf("%.10f",pie);
                System.out.print(" when i = " + i);
                System.out.println(" ");
            }
            i++;
        }
        // Final output statement
        System.out.println ("The number of iterations to get to 3.14159265 is " + savei + ".");
        System.out.printf("\n\u03C0 = %.10f",savepie);
        System.out.println(" ");
    } 
}

Here's my output in Netbeans:

The value of π is: Infinity when i = 200 
The value of π is: Infinity when i = 500 
The value of π is: Infinity when i = 1000 
The number of iterations to get to 3.14159265 is 0.0.

π = 0.0000000000 
BUILD SUCCESSFUL (total time: 0 seconds)

Here's the link to the instructions that I should follow with a Visual Logic flowchart that I tried to follow to the T. Thanks. https://www.dropbox.com/s/2m26a32afedk9yu/Lab05%20Assignment%281%29.pdf?dl=0

You have the answer in your question itself. At first iteration you have division by zero `term = (sign * 4) / ((2*i) * (2*i+1) * (2*i+2))` — Isuru, Oct 04 '18 at 03:58
Just a note for future: if you suspect a division by zero, do put a breakpoint at the division, run the code in a debugger and see what is happening there. Debugging is a valuable skill and will help you find and resolve many issues. — Sami Kuhmonen, Oct 04 '18 at 04:14
**This question might have been answered already:** https://stackoverflow.com/a/70053809/9345726 — TorbenIT, Nov 21 '21 at 11:22

score 1 · Accepted Answer · answered Oct 04 '18 at 03:57

1

You need to start your loop when i=1? The way you have it, when i=0, then term will be infinity (due to the divide-by-zero), and so pie will be infinity as well.

answered Oct 04 '18 at 03:57

moilejter

958
8
9

Alright, I'll accept this as a solution in a few minutes when Stack Overflow lets me. I was under the impression that you had to initialize the variable at 0. OK, it all seems to work, thanks. – Ryan L. Oct 04 '18 at 04:03

My simple Java pi calculator always seems to give infinity?

1 Answers1