Java编程：求解两个正整数的最大公约数与最小公倍数

package 练习12A;

import java.util.ArrayList;  
import java.util.List;  
import java.util.Scanner;  
  

public class XiTi6 {

     //输入两个正整数m和n，求其最大公因数和最小公倍数 
       
    public static void main(String args[]) {  
      
        Scanner scan = new Scanner(System.in);  
        while (true) {  
            List<Integer> list1 = new ArrayList<>();  
            List<Integer> list2 = new ArrayList<>();  
            List<Integer> list3 = new ArrayList<>();  
            System.out.println("输入两个整数");  
            int a = scan.nextInt();  
            int b = scan.nextInt();  
            int s=a;  
            int s1=b;  
            for (int i = 2; i <= a; i++) {  
                while (a % i == 0) {  
                    a = a / i;  
                    list1.add(i);  
                }  
            }  
            for (int i = 2; i <= b; i++) {