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Thread: recursion code

  1. #1
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    Default recursion code

    As I am very new to Java Programming, I'd like to make sure that this code is right!
    I was trying to make a program that computes the factorial of an input integer (args[0]) using a recursive method factorial():
    The following is my program

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

    int k=Integer.parseInt(args[0]);
    System.out.println(k + " factorial is " + factorial(k));

    }
    static double factorial(int n) {
    if (n==1) return 1;
    else return n*factorial(n-1);

    }

    }



    I hope i have written it right, however when I complile and run, there is an Exception "Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0". I tried changing static type to double and long. I also tried adding "import java.util*;" What difference would it make to this program? can someone please help, thanks.


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: recursion code

    when I complile and run, there is an Exception "Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0"
    The array you are trying to index has no elements in it. The length is zero. The first element at 0 does not exist.
    You need to pass a commandline argument to your program
    the program should test if the array that is passed to the main method is empty and if so print out a message and either exit or set a default value for the rest of the code to use.

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    Default Re: recursion code

    Initialize the length of your array first and use while statement other than if statement..there are a lot of errors of the program..
    I can fix it..let's do it in private if you want..
    email me on macabudbudcyril@yahoo.com..I am willing to help for free..

  4. #4
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    Default Re: recursion code

    If this is a student assignment you should not be doing the OPs work.

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    Default Re: recursion code

    I'm just trying to give more ideas to make it more interesting..peace..

  6. #6
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    Default Re: recursion code

    .let's do it in private if you want..
    I was referring to that part of your post.
    Why not keep it all on the forum so everyone can benefit?

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    Default Re: recursion code

    Quote Originally Posted by Norm View Post
    The array you are trying to index has no elements in it. The length is zero. The first element at 0 does not exist.
    You need to pass a commandline argument to your program
    the program should test if the array that is passed to the main method is empty and if so print out a message and either exit or set a default value for the rest of the code to use.
    Thank you very much, I noticed it is very simple after this as I learned how to pass an argument through net beans properties bar!

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    Default Re: recursion code

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

    int theNum, theFact;

    System.out.println("This program computes the factorial " +
    "of a number.");
    System.out.print("Enter a number: ");
    theNum=Console.in.readInt();

    theFact = fact(theNum);

    System.out.println(theNum + "! = " + theFact + ".");
    }

  9. #9
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    Default Re: recursion code

    you not yet dicribe [n] value

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