factorial in java stream code example

Example 1: Factorial program in java

// Factorial program using recursion
public class FactorialRecursion
{
   public static void main(String[] args)
   {
      int factorial = 1;
      int number = 6;
      factorial = factorialFunction(number);
      System.out.println("Factorial of " + number + " is : " + factorial);
   }
   static int factorialFunction(int num)
   {
      if(num == 0)
      {
         return 1;
      }
      else
      {
         return(num * factorialFunction(num - 1));
      }
   }
}

Example 2: factorial method library in java

2.4. Factorial Using Apache Commons Math
Apache Commons Math has a CombinatoricsUtils class with a static factorial method that we can use to calculate the factorial.

To include Apache Commons Math, we'll add the commons-math3 dependency into our pom:

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-math3</artifactId>
    <version>3.6.1</version>
</dependency>
Let's see an example using the CombinatoricsUtils class:

public long factorialUsingApacheCommons(int n) {
    return CombinatoricsUtils.factorial(n);
}