Need Help - StackOverflowError - Fibonacci

I'm creating a Fibonacci sequence for a program. The instructions are as follows: "Write a recursive method to compute a fibonocci series. Start at a user supplied starting point and continue 10 places."

Code:

`import javax.swing.JOptionPane;`

public class Fibonacci

{

static String series = "";

static String input = "";

public static void main(String[] args)

{

input = JOptionPane.showInputDialog(null, "Enter an integer.");

int start = Integer.parseInt(input);

fib(start, 0);

JOptionPane.showMessageDialog(null, "The series is \n" + series);

}

/** Computes a fibonocci series starting at a user supplied integer and continuing 10 places. */

public static String fib(int x, int y)

{

int i = 0;

int result = 0;

if(i < 2)

{

result = x;

y = x;

}

else

{

result = x + y;

y = x;

x = result;

}

[B] series += ", " + result;[/B]

i++;

if(i < 10)

fib(x,y);

return series;

}

}

When compiled, the method shows no errors. However, when tested, the bolded line returns the following error: "java.lang.StackOverflowError: null(in java.lang.Stringbuilder)"

As you can tell, I'm quite new to java. I don't know if I'm just not understanding the problem, or if I am, but just going about it the wrong way. Any help is appreciated.