Factorial of number in Java

Factorial of number in Java.

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Factorial of number in Java. Factorial of number is product of a number and all number below it. Example: 5! = 5 * 4 * 3 * 2 * 1 = 120.

Factorial of 3
3! = 3 * 2 * 1 = 120.

Note: The value of 0! is 1

Below you can get Factorial of number till 20.

Algorithm

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Lets see algorithm for printing Factorial of a Number.

We will see 3 ways of finding Factorial of number,

1. Recursive Implementation


2. Iterative Implementation


3. Using BigInteger for Large values.

Check Recursive Implementation Program flow below.

Java Program to Print Factorial of a number using Recursion.

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package javabypatel;

import java.math.BigInteger;

public class FindFactorialOfNumber {

 public static void main(String[] args) {
  System.out.println(factRecursive(5));
  System.out.println(factIterative(5));
  System.out.println(factorialForLargeNumbers(5));
 }

 //Recursive Implementation
 private static int factRecursive(int num){
  if(num < 0){
   return -1;
  }

  if(num == 1 || num == 0){
   return 1;
  }
  num = num * factRecursive(num-1);
  return num; 
 }

 //Iterative Implementation
 private static int factIterative(int num){
  if(num < 0){
   return -1;
  }

  int fact = 1;
  for (int i = 1; i <= num; i++) {
   fact *= i;
  }
  return fact;
 }

 //Using BigInteger for Large values
 public static String factorialForLargeNumbers(int num) {
  if(num < 0){
   return "-1";
  }
  
  BigInteger fact = new BigInteger("1");
  
  for (int i = 1; i <= num; i++) {
   fact = fact.multiply(new BigInteger(String.valueOf(i)));
  }
  return fact.toString();
 }

}

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Enjoy !!!! 

If you find any issue in post or face any error while implementing, Please comment.