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 BifIntegerMath.factorial() method:

Example 1:

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// 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);
    }
}

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Output:

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

Example 2:

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// 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);
        }
    }
}

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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-



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