BigIntegerMath factorial() function | Guava | Java

The method factorial(int n) of Guava’s BigIntegerMath class is used to find the factorial of the given number. It returns n!, that is, the product of the first n positive integers.
Syntax:

public static BigInteger factorial(int n)

Parameters: This method takes the number n as parameter whose factorial is to be found.
Return Value: This method returns the factorial of the given number n.
Exceptions: This method throws IllegalArgumentException if n < 0.
Note:

• The method returns 1 if n == 0.
• The result takes O(n log n) space, so use cautiously.
• This uses an efficient binary recursive algorithm to compute the factorial with balanced multiplies.

Below examples illustrates the BigIntegerMath.factorial() method:
Example 1:

Java

// Java code to show implementation of
// factorial() method of Guava's BigIntegerMath class

import java.math.*;
import com.google.common.math.BigIntegerMath;

class GFG {

    // Driver code
    public static void main(String args[])
    {
        int n1 = 10;

        // Using factorial(int n) method of
        // Guava's BigIntegerMath class
        BigInteger ans1 = BigIntegerMath.factorial(n1);

        System.out.println("Factorial of " + n1
                           + " is: " + ans1);

        int n2 = 12;

        // Using factorial(int n) method of
        // Guava's BigIntegerMath class
        BigInteger ans2 = BigIntegerMath.factorial(n2);

        System.out.println("Factorial of " + n2
                           + " is: " + ans2);
    }
}

Output:

Factorial of 10 is: 3628800
Factorial of 12 is: 479001600

Example 2:

Java

// Java code to show implementation of
// factorial() method of Guava's BigIntegerMath class

import java.math.*;
import com.google.common.math.BigIntegerMath;

class GFG {

    // Driver code
    public static void main(String args[])
    {

        try {
            int n1 = -5;

            // Using factorial(int n) method of
            // Guava's BigIntegerMath class
            // This should throw "IllegalArgumentException"
            // as n < 0
            BigInteger ans1 = BigIntegerMath.factorial(n1);

            System.out.println("Factorial of " + n1
                               + " is: " + ans1);
        }
        catch (Exception e) {
            System.out.println("Exception: " + e);
        }
    }
}

Output:

Exception: java.lang.IllegalArgumentException: n (-5) must be >= 0

Reference: https://google.github.io/guava/releases/21.0/api/docs/com/google/common/math/BigIntegerMath.html#factorial-int-