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Java Program to Find the Factorial of a Number
This article covers a program in Java that finds and prints the factorial of a number. The factorial of a number n is calculated as n * (n-1) * (n-2) * ... * 1. For example, the factorial of 5 is 5*4*3*2*1 or 120.
Find the factorial of a number in Java using the for loop
The question is: write a Java program to find the factorial of a number. The number must be received by the user at the runtime of the program. The answer to this question is the program given below:
import java.util.Scanner; public class CodesCracker { public static void main(String[] args) { int num, i, fact=1; Scanner s = new Scanner(System.in); System.out.print("Enter a Number: "); num = s.nextInt(); for(i=num; i>=1; i--) { fact = fact*i; } System.out.println("\nFactorial Result = " +fact); } }
The sample run of the above Java program with user input 5 is shown in the snapshot given below:
The above program can also be created in this way:
import java.util.Scanner; public class CodesCracker { public static void main(String[] args) { int fact=1; Scanner s = new Scanner(System.in); System.out.print("Enter a Number: "); int num = s.nextInt(); for(int i=num; i>=1; i--) fact = fact*i; System.out.println("\nFactorial of " +num+ " is " +fact); } }
Here is its sample run with the same user input as the previous program's sample run:
Find the factorial of a number in Java using the while loop
This program does the same job as the previous one, but was created using the while loop instead of the for
import java.util.Scanner; public class CodesCracker { public static void main(String[] args) { int fact=1; Scanner s = new Scanner(System.in); System.out.print("Enter a Number: "); int num = s.nextInt(); int i = num; while(i>=1) { fact = fact*i; i--; } System.out.println("\nFactorial of " +num+ " is " +fact); } }
The above program produces the same output as the previous program. In the above program, the following two statements:
fact = fact*i; i--;
can also be replaced with a single statement given below:
fact = fact*i--;
In the above statement, the i-- means the current value of i gets used and then decremented because of a post-increment (--) operator used.
Find the factorial in Java using a function
This program is created using a user-defined function named factorial() that takes an argument and returns the factorial result of its argument.
import java.util.Scanner; public class CodesCracker { public static void main(String[] args) { Scanner s = new Scanner(System.in); System.out.print("Enter a Number: "); int num = s.nextInt(); System.out.println("\nFactorial of " +num+ " is " +factorial(num)); } public static int factorial(int n) { int fact = 1; for(int i=n; i>=1; i--) fact = fact*i; return fact; } }
Find the factorial of a number in Java using recursion
Here is another Java program I've created to find the factorial of a number using recursion, or a recursive function. A recursive function is a function where the function calls itself from inside its definition.
import java.util.Scanner; public class CodesCracker { public static void main(String[] args) { Scanner s = new Scanner(System.in); System.out.print("Enter a Number: "); int num = s.nextInt(); System.out.println("\nFactorial of " +num+ " is " +factorial(num)); } public static int factorial(int n) { if(n>=1) return (n * factorial(n-1)); else return 1; } }
Again, the output produced by this Java program is the same as that of the previous program.
Same Program in Other Languages
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