CODEWITHSUNDEEP
javafactorial
Kacper
Kacper

Reputation: 3

Display whole calculation for getting a factorial of a number (java)

I have a simple java program calculating the factorial of a number.

Output I get after running the program:

the factorial of 5 is 120

However I would like to generate output looking like this:

5 * 4 * 3 * 2 * 1 = 120

public static int calculateFactorial(int numInput) {
    
    int factorial = 1;
    
    for (int i = 1; i <= numInput; i++) {
    factorial = factorial *i;
    }
    
    return factorial;
}

Upvotes: 0

Views: 394

Answers (3)

OrpazFishel
OrpazFishel

Reputation: 34

public static String calculateFactorial(int numInput) {
    int factorial = 1;
    String calc = "";

    for (int i = 1; i <= numInput; i++) {
      if (i != 1) {
        calc += " * ";
      }
    calc += i;
    factorial = factorial * i;
    }
    calc += " = " + factorial;
    return calc;
}

or, if you prefer x * (x-1) * ... * 1

  public static String calculateFactorial(int numInput) {
    
    int factorial = 1;
    String calc = "";

    for (int i = numInput; i > 0; i--) {
      if (i != numInput) {
        calc += " * ";
      }
    calc += i;
    factorial = factorial * i;
    }
    calc += " = " + factorial;
    return calc;
}

Upvotes: 0

Amiral ASTERO
Amiral ASTERO

Reputation: 365

Static way: Create your string in you function (this does not operate with n < 0) :

public static String calculateFactorial(int numInput) {
        StringBuilder res = new StringBuilder();
        int factorial = 1;

        for (int i = 1; i <= numInput; i++) {

            res.append(String.valueOf(i));
            if (i != numInput) {
                res.append(" * ");
            }
            factorial = factorial *i;
        }
        res.append(" = ").append(factorial);

        return res.toString();
}

Object oriented way: You can also create a Factorial class if you know about object oriented in Java (this does not operate with n < 0) :

import java.util.ArrayList;
import java.util.List;

public class Factorial {
    private int number;
    private int result;

    public Factorial(int numInput) {
        number = numInput;
        int factorial = 1;

        for (int i = 1; i <= numInput; i++) {
            factorial = factorial * i;
        }
        result = factorial;
    }

    @Override
    public String toString() {
        StringBuilder res = new StringBuilder();
        for (int i = 0; i <= number; i++) {

            res.append(i);
            if (i != number) {
                res.append(" * ");
            }
        }
        res.append(" = " + result);

        return res.toString();
    }
}

Then you can use a System.out.println(new Factorial(n)); to print the result

Upvotes: 1

Oleg Cherednik
Oleg Cherednik

Reputation: 18245

public static String calculateFactorialStr(int val) {
    String res = IntStream.range(0, val)
                          .map(i -> val - i)
                          .mapToObj(String::valueOf)
                          .collect(Collectors.joining(" * "));
    return res + " = " + calculateFactorial(val);
}

public static long calculateFactorial(int val) {
    long res = 1;

    for (int i = 2; i <= val; i++)
        res *= i;

    return res;
}

Upvotes: 2

Related Questions