how to handle Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index 4 out of bounds for length 0 at Factorl.main(Factorl.java:

Question

class Factorl
{
    public static void main(String args[])

    {
              long n,fact=1;       

              n=Long.parseLong(args[0]);

          for(int i=1;i<=n;i++)
          {
                 fact=fact*i;
          }

          System.out.println("fact="+fact);
    }
}

its showing Exception in thread "main"

java.lang.ArrayIndexOutOfBoundsException: 0 at Factorl.main

How are you running `Factorl`? Posted code should not generate posted exception; please clarify. `args` may well be empty, but the "index 4" part makes no sense. — Elliott Frisch, Aug 30 '19 at 06:24
Welcome to Stackoverflow. Please refer https://stackoverflow.com/help/how-to-ask and https://stackoverflow.com/help/mcve . Put more details of the issue that you are facing. — Nagama Inamdar, Aug 30 '19 at 06:53
As commented by @ElliottFrisch looks like you are not passing any argument to your main method.Use `javac filenamehere.java` to compile and `java filenamehere arg` to run — Imran, Aug 30 '19 at 06:54
Is the the code you're running to get this error? i doubt it: the only index i see is 0. — Maurice Perry, Aug 30 '19 at 07:05
you should pass a command-line argument as an input for this — MangduYogii, Aug 30 '19 at 07:06

score 0 · Answer 1 · answered Aug 30 '19 at 07:11

Because you using command-line arguments as an input in your program line

  n=Long.parseLong(args[0]);

Here you should pass a value for running a program like this

  compile by > javac Factorl.java  
   run by > java Factorl 5

    Output:
    fact=120

Prashant · Answer 2 · 2019-08-30T08:16:37.140

Your args array could be empty if nothing is passed to it (ref). Make a check for its emptiness.

class Factorl {
    public static void main(String args[]) {
        long n, fact = 1;
        if (args.length != 1) {
            System.out.println("Factorial for what?");
            return;
        }
        n = Long.parseLong(args[0]);
        for (int i = 1; i <= n; i++) {
            fact = fact * i;
        }
        System.out.println("fact=" + fact);
    }
}

I do not personally think that you would be calculating the factorial of a Long. The factorials grow very quickly. Note that 20! is 2.432902e+18. Thats at huge number. Now you can refer @MangduYogii's answer for "How to pass command line arguments".

how to handle Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index 4 out of bounds for length 0 at Factorl.main(Factorl.java:

2 Answers2