我这做了一个很简单的猜数字游戏，程序它还有点小瑕疵，求改进

Question

问题遇到的现象和发生背景

大二学生做的简单程序，遇到的难题，解答

问题相关代码

package just;
import java.util.Scanner;
class G{
    static int re=-1;
     public void G(){
         int n=(int)(Math.random()*10000);
        int n1=n/1000,n2=n/100%10,n3=n/10%10,n4=n%10;
        while(n1==n2||n1==n3||n1==n4||n2==n3||n2==n4||n3==n4){
            n=(int)(Math.random()*10000);
        }
        System.out.println("Start The Game");
        int se=1,gn;
        while(se!=0){
        Scanner build=new Scanner(System.in);
        System.out.println("请输入你猜测的四位数");
        gn=build.nextInt();
        while(gn<1000||gn>9999){
            System.out.println("输入错误，请重新输入1个4位数：");
            gn=build.nextInt();
        }
        int g1=gn/1000,g2=gn/100%10,g3=gn/10%10,g4=gn%10;
        int b=0,a=0;
        while(g1==g2||g1==g3||g1==g4||g2==g3||g2==g4||g3==g4){
            System.out.println("有重复数字，请重新输入：");
            gn=build.nextInt();
            g1=(gn/1000);g2=(gn/100%10);g3=(gn/10%10);g4=(gn%10);
        }
        if(g1==n1){
            a++;
        }else  if(g1==n2||g1==g3||g1==g4){
                b++;
              }
        
        if(g2==n2){
            a++;
        }else  if(g2==n1||g2==n3||g2==n4){
                b++;
            }
        
         if(g3==n3){
             a++;
         }else if(g3==n1||g3==n2||g3==n4){
                 b++;
             }
         
         if(g4==n4){
           a++;
         }else if(g4==n2||g4==n3||g4==n4){
                     b++;
             }
         if(a==4){
             System.out.println("锣鼓喧天，鞭炮齐鸣     您猜对啦！！！");
             System.out.println("是否继续游戏（退出请输入0）");
             re=build.nextInt();
             if(re==0&&re!=-1){
                 break;
             }else{
                    new G();
                    G.re=-1;
                }
         }
         else
         {
         System.out.println(a+"A"+b+"B");
         System.out.println("是否继续游戏（退出请输入0）");
         se=build.nextInt();
         }
        }    
     }
}
public class guess {
    public static void main(String[] args) {
        G g=new G();
        g.G();
    }
}

运行结果的瑕疵

我想要达到的结果

解决上面截图中，在输入时同样的四个数只是位置不同，但是却出现结果的偏差的问题

Answer 1

import java.util.Scanner;
class G{
    static int re=-1;
    public void G(){
        int n=(int)(Math.random()*10000);
        int n1=n/1000,n2=n/100%10,n3=n/10%10,n4=n%10;
        while(n1==n2||n1==n3||n1==n4||n2==n3||n2==n4||n3==n4){
            n=(int)(Math.random()*10000);
            n1=n/1000;
            n2=n/100%10;
            n3=n/10%10;
            n4=n%10;
        }
        System.out.println("Start The Game");
        int se=1,gn;
        while(se!=0){
            Scanner build=new Scanner(System.in);
            System.out.println("请输入你猜测的四位数");
            gn=build.nextInt();
            while(gn<1000||gn>9999){
                System.out.println("输入错误，请重新输入1个4位数：");
                gn=build.nextInt();
            }
            int g1=gn/1000,g2=gn/100%10,g3=gn/10%10,g4=gn%10;
            int b=0,a=0;
            while(g1==g2||g1==g3||g1==g4||g2==g3||g2==g4||g3==g4){
                System.out.println("有重复数字，请重新输入：");
                gn=build.nextInt();
                g1=(gn/1000);g2=(gn/100%10);g3=(gn/10%10);g4=(gn%10);
            }
            System.out.println(g1+"  "+g2+"   "+g3+"   "+g4);
            if(g1==n1){
                a++;
            }else  if(g1==n2||g1==g3||g1==g4){
                b++;
            }

            if(g2==n2){
                a++;
            }else  if(g2==n1||g2==n3||g2==n4){
                b++;
            }

            if(g3==n3){
                a++;
            }else if(g3==n1||g3==n2||g3==n4){
                b++;
            }

            if(g4==n4){
                a++;
            }else if(g4==n2||g4==n3||g4==n1){
                b++;
            }
            if(a==4){
                System.out.println("锣鼓喧天，鞭炮齐鸣     您猜对啦！！！");
                System.out.println("是否继续游戏（退出请输入0）");
                re=build.nextInt();
                if(re==0&&re!=-1){
                    break;
                }else{
                    new G();
                    G.re=-1;
                }
            }
            else
            {
                System.out.println(a+"A"+b+"B");
                System.out.println("是否继续游戏（退出请输入0）");
                se=build.nextInt();
            }
        }
    }
}
public class guess {
    public static void main(String[] args) {
        G g=new G();
        g.G();
    }
}