BigFactorial.java

// JAVA program to compute factorial 
// of big numbers 
class GFG { 
	
	// This function finds factorial of 
	// large numbers and prints them 
	static void factorial(int n) 
	{ 
		int res[] = new int[500]; 

		// Initialize result 
		res[0] = 1; 
		int res_size = 1; 

		// Apply simple factorial formula 
		// n! = 1 * 2 * 3 * 4...*n 
		for (int x = 2; x <= n; x++) 
			res_size = multiply(x, res, res_size); 

		System.out.println("Factorial of given number is "); 
		for (int i = res_size - 1; i >= 0; i--) 
			System.out.print(res[i]); 
	} 
	
	// This function multiplies x with the number 
	// represented by res[]. res_size is size of res[] or 
	// number of digits in the number represented by res[]. 
	// This function uses simple school mathematics for 
	// multiplication. This function may value of res_size 
	// and returns the new value of res_size 
	static int multiply(int x, int res[], int res_size) 
	{ 
		int carry = 0; // Initialize carry 

		// One by one multiply n with individual 
		// digits of res[] 
		for (int i = 0; i < res_size; i++) 
		{ 
			int prod = res[i] * x + carry; 
			res[i] = prod % 10; // Store last digit of 
								// 'prod' in res[] 
			carry = prod/10; // Put rest in carry 
		} 

		// Put carry in res and increase result size 
		while (carry!=0) 
		{ 
			res[res_size] = carry % 10; 
			carry = carry / 10; 
			res_size++; 
		} 
		return res_size; 
	} 

	// Driver program 
	public static void main(String args[]) 
	{ 
		factorial(100); 
	} 
} 
//This code is contributed by VickyJsr