CODEWITHSUNDEEP
java
user6790886
user6790886

Reputation:

Why does calculating pi using a loop not work correctly?

We got an assignment where we have to calculate the value of pi using the formula pi/4=1-1/3+1/5-1/7+1/9-1/11...(using 100 terms) but it doesn't seem to run the while-loop for some reason. We're students who have no prior experience of writing code and are just starting.

double pi = 1;
int count = 0;
int n = 3;

while (count < 100) {
    if ((count&1) == 0) {  
        pi = pi - 1 / n;
    } else {
        pi = pi + 1 / n;
    }
    n = n + 2;
    count++;
}
out.print(pi*4);   //why is it printing out pi=1?????

Upvotes: 1

Views: 201

Answers (1)

progyammer
progyammer

Reputation: 1508

The problem is you do not type cast. pi is double but 1/n returns int, since both the denominator and numerator are integers. This happens in JAVA. Basically, every time, 1/n which is actually fractional, returns 0 (int) for every n > 1 due to lack of type casting. So pi's value is always 1 and in the end pi*4 displays 4.0. So you have to convert (cast) the numerator or the denominator as fractional (double) to make 1/n fractional.

To solve the problem, change the statements 

pi = pi + 1 / n;
pi = pi - 1 / n;

to 

pi = pi + 1.0 / (double) n;
pi = pi - 1.0 / (double) n;

This displays the output as 3.1514934010709914.

Upvotes: 7

Related Questions