[RESOLVED] different answer

[vb_student]

Hello

i was tring to figure out what the result of factorial for 21 using the following code.

java code

import java.io.*;
/**
 *
 * @author  
 */
public class mywelcome {
  public static void main (String[] args) throws IOException
  {
    BufferedReader userin = new BufferedReader 
        (new InputStreamReader(System.in));
    String inputData;
    long    N, fact = 1; 

    System.out.println( "Enter N:" );
    inputData = userin.readLine();
    N         = Integer.parseInt( inputData );

    if ( N >= 0 )
    {
      while ( N > 1 )    
      {
        fact = fact * N;
        N    = N - 1;
      }
      System.out.println( "factorial is " + fact );
    }
    else
    {
      System.out.println("N must be zero or greater");
    }
  }
}

when i use the code in the netbeans environment, i get the answer -4249290049419214848
but the following link states the answer should be 51090942171709440000

http://chortle.ccsu.edu/CS151/Notes/...r+greater&N=20

can you guys tell me why the difference?

[System_Error]

I don't agree with what how you're doing it. Simply use a for loop:

long total = 1;
for (int index=21; index >=1; --index)
{
  total *=index;
}

Something along those lines... You can use recursion, but I'd prefer this method.

[ComputerJy]

That's JavaScript, it's totally different than java besides "51090942171709440000" is very big to contain in a "long" variable,
try this:

import java.io.* ;

/**
 *
 * @author  Moyeen
 */
public class My
{
  public static void main (String[] args) throws IOException {
    BufferedReader userin = new BufferedReader(new InputStreamReader(System.in)) ;
    String inputData ;
    int N; 
    double fact = 1 ;

    System.out.println("Enter N:") ;
    inputData = userin.readLine() ;
    N = Integer.parseInt(inputData) ;

    if (N >= 0) {
      while (N > 1) {
        fact = fact * N ;
        N-- ;
      }
      System.out.println("factorial is " + fact) ;
    }
    else {
      System.out.println("N must be zero or greater") ;
    }
  }
}

[vb_student]

thanks for the replies

i have just started on java, and am going through this tutorial on central conneticut state university's web tutorial on java

[ComputerJy]

Good, welcome to java
if you are done, please mark the thread resolved

[vb_student]

done. thanks again

[ComputerJy]

this is not how you mark a thread resolved!
Click on "Thread Tools" and select "Mark Thread Resolved"

[CornedBee]

double is potentially inaccurate. Use java.math.BigInteger instead. Note that you have to use the class's member functions instead of normal mathematical operators, though.

[vb_student]

done