Java阶乘

public class Factorial{
 private long n;
 private long s=1;
 public Factorial(long num){
 n=num;
 }
 public void calculateFac(){
  for(long i=2;i<=n;i++){
   
       s=s*i;
       
  
  }
  //System.out.println(s);
  //return s;
 }
 public long getNum(){
 return s;
}
 public static void main(String[] args){

 long n = Long.parseLong(args[0]);

 Factorial Fac = new Factorial(n);
 
 Fac.calculateFac();
 //Fac.calculateFac(n);
 System.out.println(Fac.getNum());

 }

}