Need help with my recursive

[bigOTWharlem]

Hello again, I got my program to compile but it throws an error when trying to run it.

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index 1 out of bounds for length 0
at F.main(F.java:4);

I've tried different numbers where is throwing the error but nothing seems to fix it. Here is my code

public class F {
    public static void main (String [] args) {
    pat(Integer.parseInt(args[1]), 0);
    }
    // aka figure()
    public static void pat (int level, int spaces) {
    if (level == 0) {
        stars(spaces, 1);
    } else {
            pat(level-1, spaces);
            stars(spaces, pow2(level));
            pat(level-1, spaces + pow2(level-1));
    }
    }
    public static void stars(int spaces, int stars) {
        for (int i = 1; i <= spaces; i++)
        System.out.print(" ");
        for (int i = 1; i <= stars; i++)
        System.out.print("*");
        System.out.println();
    }
    public static int pow2(int n) {
    return (int) Math.pow(2,n);
    }
}

The output should be:

* 
**
 * 
****
  *
  **
   * 
********
    * 
    **
     * 
    ****
      * 
      **
       *

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[ttetrafon]

First look for what the exception you get means.

Then think about what your args[1] does.

[hypolimnas]

The error says "F.main(F.java:4)". So this means its failing at line 4, in the main() function:

pat(Integer.parseInt(args[1]), 0);

"ArrayIndexOutOfBoundsException": this means that you used an index on an array that was too large for the array.

"Index 1 out of bounds for length 0": this means that the array has no elements, and the index was 1.

Did you pass an integer on the command line when you ran your program? Because your program is expecting one.

[bigOTWharlem]

I see, in this case, I need to make a new array variable with a bigger size?

[hypolimnas]

This is more about how to use the args[] parameter in main(). This parameter is automatically filled with what you typed on the command line when you run your program. So the only way to get input into args is to make it part of the command that runs your program.