Factorial.java

package test;

public class Factorial {

	public static void main(String[] args) {
	       
		System.out.println(factorial(-1));
		System.out.println(factorial(0));
		System.out.println(factorial(1));
		System.out.println(factorial(2));
		System.out.println(factorial(3));
		System.out.println(factorial(5));
		System.out.println(factorial(6));

	}
	static long factorial(int i)
	{
		if(i<0 || i>20)
		{
			System.out.print("Give me another number");
			return -1;
		}
		long rezalt=1;
		
		for(int k=2;k<=i;k++)
		{
			rezalt*=k;
		}
		return rezalt;
	}

}