欧几里得算法求最大公约数

import java.util.Scanner;
public class GCD{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in); 
        while(true){
            try{
                System.out.println("Please input first number:");
                int firstNum = Integer.valueOf(sc.next());
                System.out.println("Please input second number:");
                int secondNum = Integer.valueOf(sc.next());
                System.out.println("The gcd of " + firstNum + " and " + secondNum + " is: " + gcd(firstNum,secondNum)); 
            }catch(Exception e){
                System.out.println("The Input Just now is not a int type,Pls input again:");
                continue;
            }
        }
    }


    public static int gcd(int p, int q){
        if(0 == q){
            return p;
        }
        int r  = p % q;
        return gcd( q, r);
    }


    public static <T> String getType(T t){ 
        if(t instanceof Integer){ 
            return "int"; 
        }else if(t instanceof String){ 
            return "string"; 
        }else{ 
            return " do not know"; 
        } 
    }
}