define a package factorial in java code example

Example: 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);
}