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Thread: Recursion help

  1. #1
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    Default Recursion help

    Hi everyone, so I'm still trying to figure out how to get my recursive function to work to calculate my sine so I figured I'd start with a factorial function and work my way up, adding the necessary parts. I looked at http://www.javaprogrammingforums.com...-concepts.html but I can't get any of the code to work.

    I get these errors
    ftest.java:1: class, interface, or enum expected
    public static int interativeFactorial(int n)
                  ^
    ftest.java:4: class, interface, or enum expected
            for(int i = 1; i < n; i++)
            ^
    ftest.java:4: class, interface, or enum expected
            for(int i = 1; i < n; i++)
                           ^
    ftest.java:4: class, interface, or enum expected
            for(int i = 1; i < n; i++)
                                  ^
    ftest.java:7: class, interface, or enum expected
            }
            ^
    ftest.java:9: class, interface, or enum expected
    }
    ^
    6 errors

    All I'm using is

    public static int interativeFactorial(int n)
    {
            int answer = 1;
            for(int i = 1; i < n; i++)
            {
                    answer *= i;
            }
            return answer;
    }
    }

    I've tried adding in
    public class ftest
    {
    public static int interativeFactorial(int n)
    {
            int answer = 1;
            for(int i = 1; i < n; i++)
            {
                    answer *= i;
            }
            return answer;
    }
    }

    but then I get the error

    Exception in thread "main" java.lang.NoSuchMethodError: main

    so then I tried putting in
    public class ftest
    {
    public static void main(String args[])
    {
    public static int interativeFactorial(int n)
    {
            int answer = 1;
            for(int i = 1; i < n; i++)
            {
                    answer *= i;
            }
            return answer;
    }
    }
    }

    then I just get more errors!
    ftest.java:5: illegal start of expression
    public static int interativeFactorial(int n)
    ^
    ftest.java:5: illegal start of expression
    public static int interativeFactorial(int n)
           ^
    ftest.java:5: ';' expected
    public static int interativeFactorial(int n)
                 ^
    ftest.java:5: '.class' expected
    public static int interativeFactorial(int n)
                                              ^
    ftest.java:5: ';' expected
    public static int interativeFactorial(int n)
                                               ^
    5 errors

    I'm pretty lost about what to do at this point if I can't even get this to compile and work right. Any clarification would be appreciated!


  2. #2
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    Default Re: Recursion help

    First off this is not recursion, you are using a loop, recursion relies on recalling the same method until some condition is met.

    Your code, although not recursion is fine, except you need a main method. All classes are a series of methods, main is the entry point of a program. You don't define a method in main, instead you call methods in main. Methods are created outside of the main method

    public class blah{
      public static void hello(){
        System.out.println("hello");
      }
      public static void main(String[] args){
        hello();
      }
    }

    Try compiling and runnning that and see if it helps you a bit with what you did wrong in your code.

  3. The Following User Says Thank You to sunde For This Useful Post:

    Actinistia (March 21st, 2011)

  4. #3
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    Default Re: Recursion help

    This is an example of a program to recursively add two numbers.

    public class Add{
      public static int add(int x, int y){
        if(y == 0){
          return x;
        }
        else{
          return add(x + 1, y - 1);
        }
      }
      public static void main(String[] args){
        System.out.println(add(5, 6));
      }
    }

  5. #4
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    Default Re: Recursion help

    Quote Originally Posted by sunde View Post
    First off this is not recursion, you are using a loop, recursion relies on recalling the same method until some condition is met.

    Your code, although not recursion is fine, except you need a main method. All classes are a series of methods, main is the entry point of a program. You don't define a method in main, instead you call methods in main. Methods are created outside of the main method

    public class blah{
      public static void hello(){
        System.out.println("hello");
      }
      public static void main(String[] args){
        hello();
      }
    }

    Try compiling and runnning that and see if it helps you a bit with what you did wrong in your code.
    Thanks for clarifying that, I stated that it was recursion based off the topic of the tutorial I found the code in. The example code was very helpful to show how recursion actually works. I think I understand why it didn't work now. I'm still pretty new to java and all, so thanks you for all your help!

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