In this post we will learn about Java program to find factorial of a number.
Before Witting java program let’s understand what is Factorial number?
What is Factorial Number?
In mathematics language, we can say that the factorial of a non-negative integer n, denoted by n! is the product or multiplication of all positive integers less than or equal to n.
For example, 5 ! = 5 × 4 × 3 × 2 × 1 = 120.
The factorial of a negative number doesn’t exist. And the factorial of 0 is 1
We will solve this problem statement using below 2 approaches:
- Using for loop
- Using recursion
Example 1:
Using for loop
Below source code of the Java Program reads number from the user and finds factorial value using for loop
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package com.kkjavatutorials.client; import java.util.Scanner; /** * @author KK JavaTutorials * This Java program is all about How to find factorial of a input number using for loop */ public class ClientTest1 { public static void main(String[] args) { try (Scanner scanner = new Scanner(System.in)) { // Take a number from keyboard using Scanner System.out.println("Enter a Number:"); int number = scanner.nextInt(); int fact = findFactorial(number); System.out.println("Factorial of input " + number + " is " + fact); } catch (Exception e) { System.out.println("Please Enter valid number.."); e.printStackTrace(); } } //find factorial of a number using for loop private static int findFactorial(int number) { //Validation for negative number if(number<0){ throw new RuntimeException("The factorial of a negative number doesn’t exist.try With positive number"); } int factorial = 1; for (int i = number; i >= 1; i--) { factorial = factorial * i; } return factorial; } } |
Example 2:
Using recursion
Below source code of the Java Program reads number from the user and finds factorial value With using Recursion.
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package com.kkjavatutorials.client; import java.util.Scanner; /** * @author KK JavaTutorials * This Java program is all about How to find factorial of a input umber using recursion */ public class ClientTest2 { public static void main(String[] args) { try (Scanner scanner = new Scanner(System.in)) { // Take a number from keyboard using Scanner System.out.println("Enter a Number:"); int number = scanner.nextInt(); int fact = findFactorial(number); System.out.println("Factorial of input " + number + " is " + fact); } catch (Exception e) { System.out.println("Please Enter valid number.."); e.printStackTrace(); } } //find factorial of a number using recursion private static int findFactorial(int number) { //Validation for negative number if(number<0){ throw new RuntimeException("The factorial of a negative number doesn’t exist.try With positive number"); } //base case condition if (number == 1 || number == 0) { return 1; } else { return number * findFactorial(number - 1); } } } |
I have tested both programs for few inputs as below. You may check for other input as well
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Enter a Number: 4 Factorial of input 4 is 24 Enter a Number: 5 Factorial of input 5 is 12 Enter a Number: 10 Factorial of input 10 is 3628800 |
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