Find Factorial of a Number in Java.

In this article, we will learn multiple approaches to finding the factorial of a number in Java Programming. Before moving to the code part lets us first understand what is Factorial and how to calculate it.

What is the Factorial of a Number?

Factorial is a mathematical operation that is used to calculate the product of all positive integers from 1 to a given positive integer n.

It is denoted by the symbol "!" and is defined as follows:

n! = n x (n-1) x (n-2) x ... x 3 x 2 x 1

For example, the factorial of 5 is calculated as:

5! = 5 x 4 x 3 x 2 x 1 = 120
The factorial of 0 is defined to be 1 by convention, that is: 0! = 1

We can find the factorial of a number using the following approaches:

Find Factorial using for loop.

In this approach, we use a for loop to multiply each number from 1 to n, where n is the number for which we need to find the factorial.

Java Code:

//Java code to find factroil of a number using for loop
import java.util.Scanner;

public class HelloWrold {

  public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    System.out.print("Enter a number: ");
    int n = input.nextInt();
    int factorial = 1;
    for (int i = 1; i <= n; i++) {
      factorial *= i;
    }
    System.out.println("Factorial of " + n + " is " + factorial);
  }
}

Output:

Enter a number: 5
Factorial of 5 is 120

Time Complexity: O(n)
Space Complexity: O(1)

Find Factorial using Recursion.

In this approach, we use a recursive function to find the factorial of a number. A recursive function is a function that calls itself.

Java Code:

//Java code to find factroil of a number using Recursion
import java.util.Scanner;

public class Factorial {

  public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    System.out.print("Enter a number: ");
    int n = input.nextInt();
    int factorial = fact(n);
    System.out.println("Factorial of " + n + " is " + factorial);
  }

  public static int fact(int n) {
    if (n == 0) {
      return 1;
    }
    return n * fact(n - 1);
  }
}

Output:

Enter a number: 5
Factorial of 5 is 120

Time Complexity: O(n)
Space Complexity: O(n)

Find Factorial using a while loop.

In this approach, we use a while loop to multiply each number from 1 to n, where n is the number for which we need to find the factorial.

Java Code:

//Java code to find factroil of a number using while loop
import java.util.Scanner;

public class Factorial {

  public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    System.out.print("Enter a number: ");
    int n = input.nextInt();
    int factorial = 1;
    int i = 1;
    while (i <= n) {
      factorial *= i;
      i++;
    }
    System.out.println("Factorial of " + n + " is " + factorial);
  }
}

Output:

Enter a number: 10
Factorial of 5 is 3628800

Time Complexity: O(n)
Space Complexity: O(1)

Find Factorial of a Number in Java.

What is the Factorial of a Number?

Find Factorial using for loop.

Find Factorial using Recursion.

Find Factorial using a while loop.

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