Calcular N Factorial En Java

What is a factorial?

The factorial of a non-negative integer n, denoted by n!, is the product of all positive integers less than or equal to n. For example:

• 5! = 5 × 4 × 3 × 2 × 1 = 120
• 4! = 4 × 3 × 2 × 1 = 24
• 3! = 3 × 2 × 1 = 6
• 2! = 2 × 1 = 2
• 1! = 1
• 0! = 1 (by definition)

Factorials are used in combinatorics, probability, algebra, and other mathematical fields. In Java programming, you can calculate factorials using loops, recursion, or built-in methods.

Calculating factorial in Java

There are several ways to calculate factorials in Java:

1. Using iterative approach with a for loop
2. Using recursive method
3. Using Java Streams
4. Using BigInteger for large numbers

Each method has its advantages and disadvantages in terms of performance, readability, and handling large numbers.

Java code examples

1. Iterative approach with for loop

public class Factorial {
    public static long factorial(int n) {
        if (n < 0) {
            throw new IllegalArgumentException("Factorial is not defined for negative numbers");
        }
        long result = 1;
        for (int i = 1; i <= n; i++) {
            result *= i;
        }
        return result;
    }

    public static void main(String[] args) {
        System.out.println("5! = " + factorial(5)); // Output: 5! = 120
    }
}

2. Recursive approach

public class Factorial {
    public static long factorial(int n) {
        if (n < 0) {
            throw new IllegalArgumentException("Factorial is not defined for negative numbers");
        }
        if (n == 0 || n == 1) {
            return 1;
        }
        return n * factorial(n - 1);
    }

    public static void main(String[] args) {
        System.out.println("4! = " + factorial(4)); // Output: 4! = 24
    }
}

3. Using Java Streams

import java.util.stream.IntStream;

public class Factorial {
    public static long factorial(int n) {
        if (n < 0) {
            throw new IllegalArgumentException("Factorial is not defined for negative numbers");
        }
        return IntStream.rangeClosed(1, n)
                       .reduce(1, (x, y) -> x * y);
    }

    public static void main(String[] args) {
        System.out.println("3! = " + factorial(3)); // Output: 3! = 6
    }
}

4. Using BigInteger for large numbers

import java.math.BigInteger;

public class Factorial {
    public static BigInteger factorial(int n) {
        if (n < 0) {
            throw new IllegalArgumentException("Factorial is not defined for negative numbers");
        }
        BigInteger result = BigInteger.ONE;
        for (int i = 1; i <= n; i++) {
            result = result.multiply(BigInteger.valueOf(i));
        }
        return result;
    }

    public static void main(String[] args) {
        System.out.println("20! = " + factorial(20));
        // Output: 20! = 2432902008176640000
    }
}