JAvaは2つの数の最大公約数と最大公倍数を求めます

import java.util.Scanner;
public class Test01 {
    public static void main(String args[]) {
        Scanner scanner=new Scanner(System.in);
        System.out.println("        ");
        int n1 =scanner.nextInt();
        int n2 =scanner.nextInt();
        int first=java.lang.Math.max(n1,n2);
        int second=java.lang.Math.min(n1,n2);
        System.out.println("          ："+'
'+"1.     "+'
'+"2.   "+'
'+"3.   ");
        int method=scanner.nextInt();
        System.out.print(n1+","+n2+"       ："); 
        switch(method){
        case 1:
            System.out.println(method1(first,second));break;
        case 2:
            System.out.println(method2(first,second));break;
        case 3:
            System.out.println(method3(first,second));break;
        }
        System.out.println(n1+","+n2+"       "+(n1*n2)/method1(first,second));
    }   
    //           
    public static int method1(int first,int second){
        if(second==0)
            return first;
        return method1(second,first%second);

    }
    //         
    public static int method2(int first ,int second) {

        int i=first-second;
        while(i!=0) {
            first=second;
            second=i;
            i=first-second;
        }
        return second;
    }
    //         
    public static int method3(int first ,int second) {
        int i= second;
        while(i>0) {
            if(first%i==0 && second%i==0) break;
            i--;
        }
        return i;
    }
}