Creating class object to do factorial recursion? [closed]

Answer 1

No, you created a method, fact(int n) that calculates the factorial.

You should create a new class with a method that calculates the factorial. An object of the class would be instantiated and then, the method that calculates the factorial would be invoked from the class object.

Example:

// outside the while loop instantiate your class object for
// dealing with factorial computations
Factorial factorial = new Factorial();

// inside the while loop, instantiate your method for 
// computing factorial of "n", invoking your factorial 
// computation method that is defined inside your class
int result = factorial.computeFactorial(n);

Answer 2

If you want to make a class object then remove static from your method Also it would be better if you use dynamic programming approach for solving this problem.

import java.util.*;
import java.io.*;

public class Assignment2A {

    public static void main(String[] args){
        Assignment2A x = new Assignment2A();
        x.askForOutput();
    }

    int fact(int n){
        int output;                 //sets the output as int
        long startTime = System.nanoTime();     //gets the start time of the cpu
        long taskTime = System.nanoTime()-startTime;    //gets the task time
        if (n==0){                      //if the input is 0, system exits
            System.out.println("Exiting Program");      
            System.out.println("Task Time: "+taskTime+ " nanoseconds."); //displays cpu time
            System.exit(0);
        }
        else if(n==1){
            return 1;           //if input is 1, the factorial of 1 is 1
        }
        output = fact(n-1)*n;   //recursive method for factorial
        return output;

    }
    public void askForOutput(){
        Scanner scan = new Scanner(System.in); //sets up scanner
        boolean correct = true;             //sets up boolean operation
        while(true){
            try{                                //try catch operation
                System.out.println("Welcome to the factorial function");
                System.out.println("Please enter a number or press 0 to exit");
                long startTime =System.nanoTime();
                System.out.println("Start Time: "+startTime+" nanoseconds."); //display the start time

                int n = scan.nextInt();             //scans the input
                int factorial= fact(n);             
                System.out.println("The Factorial of the number entered is: " + factorial);

                long taskTime = System.nanoTime() - startTime;
                System.out.println("Task Time: "+taskTime+" nanoseconds.\n\n");

            }catch(Exception e){                //checks if the input is a string or character
                System.out.println("That is not a number!");    //displays that the input is invalid
                long startTime =System.nanoTime();
                long taskTime = System.nanoTime() - startTime;
                System.out.println("Task Time: "+taskTime+" nanoseconds.");
                System.exit(0);         //exits the program
            }
        }
    }


}

Answer 3

If you want this to be in a separate class, just encapsulate your fact() method in a new class. Note, however, that your printout of the time taken is incorrect - it merely computes the time for the final entry into the recursive method.

public class Factorial {

   public static int compute( int val ) {
      long startTime = System.nanoTime();
      int result = fact( val );
      long taskTime = System.nanoTime()-startTime;
      System.out.println("Task Time: "+taskTime+ " nanoseconds.");
   }

   protected static int fact( int val ) {
      if (n==1){
         return val;
      }
      return fact(val-1)*val;
   }
}

then in you main,

 int answer =  Factorial.compute(value);