factorial in java library code example

Example 1: how to make factorial in java

class fact{
	static int fac(int n){
		int ans =1;
		for(int i=1; i<=n; i++){
			ans = ans*i;
		}
		return ans;
	}

	public static void main (String[] args){
		int f = 5;
		System.out.println(fac(f));
	}
}

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);
}