Exception in thread "main" java.lang.StackOverflowError when making Fibonnaci method

Question

I am a new Java user. This is my first question. I am just making a fibonacci number generator but got this error:

Exception in thread "main" java.lang.StackOverflowError
at com.intro.javaintro.JavaIntro.fib(JavaIntro.java:11) // This line is repeat 1024 times

Here is my code:

public class JavaIntro {
    static int fib(int n) {
        int i = 0;
        if (n == 1) {
            i = 0;
        } else if (n == 1) {
            i = 1;
        } else {
            i = fib(n - 1) + fib(n - 2);
        }
        return i;
    }
    public static void main(String[] args) {
        System.out.println(fib(5));
    }
}

Plz help me

Answer 1

stackoverflow error means your recursion isn't ending properly

in your code the first two if statements are supposed to be your exits. since you are checking n==1 twice,

if n = 3

fib(1) and fib(2) will be called fib(1) will be closed but fib(2) wont

fib(2) will call fib(1) and fib(0)

fib(0) will call fib(-1) and fib(-2)...

fibonacci series look sth like this: 1 1 2 3 5 8 13...

considering that you are trying to get the nth fibonacci number your condition should look sth like this

if n is 1 or 2 returns 1

if n is higher than 2 returns sum of n-1 and n-2

your condition should look sth like this

       if(n==1||n == 2) {
            i = 1;
       } else {
            i = fib(n - 1) + fib(n - 2);
       }