why this code send me Stackoverflow in java

Question

I've try to use long and double with c, k, n variables but netbeans shows me a stack overflow error:

public class Main {

public static void main(String[] args) {
   double c=0; //combinatorial
   double n=5;
   double k=15;

   c= factorial(n)/(factorial(k)*factorial(n-k));

   System.out.print(n+" combinatorial "+k+" between "+c+"\n");

}

    static double factorial (double number) {
        if (number == 0) 
            return 1;
          else 
            return number * factorial(number-1);
   }
}

Exception in thread "main" java.lang.StackOverflowError
    at co.combinatorial.Main.factorial(Main.java:26)
    at co.combinatorial.Main.factorial(Main.java:29)
    at co.combinatorial.Main.factorial(Main.java:29)
    at co.combinatorial.Main.factorial(Main.java:29)
......

Java Result: 1

Do I have to use integer literals or long.parselong

What I am doing wrong?

Answer 1

From the initial values, nk = -10. Since this is less than 0, your factorial method will never return

Answer 2

(number == 0) may not happen due to binary representation of number. Even with some tolerance level added, it is still incomplete this way. You may need negative number conformance. (10-10 maybe not zero)

Each time it goes deeper in function stack because of recursivity, it consumes more memory for function variables and parameters until java cannot plea more from operating system.

Answer 3

c= factorial(n)/(factorial(k)*factorial(nk));

For n=5 and k=15,

factorial(nk) would become: factorial(-10)

and then..

number*factorial(number-1) would give us: -10*factorial(-11),

and like this it would

continue indefinitely never reaching 0.

hence the stack will overflow.