什么在我的代码是错误的（Java字符输入的初学者）

Question

import java.util.Scanner; 
public class Application { 

public static void main(String[] args) { 
    do { 
    System.out.println("What is the command keyword to exit a loop in Java?\na. int\nb. continue\nc. break\nd. exit\nEnter your choice"); 
    Scanner ans = new Scanner(System.in); 
    char ans = sc.next().charAt(0); 
    if(ans=='c') 
     System.out.println("Correct"); 
    else 
     System.out.println("Wrong! Presss Y to try again."); 
    Scanner redo = new Scanner(System.in); 
    char redo = sc.next().charAt(0); 
    } 
    while(redo=='y'); 
} 

}

我刚开始学习Java，可以请你告诉我，什么是错在我的代码，以及如何改进呢？谢谢

这是我收到的错误。

Exception in thread "main" java.lang.Error: Unresolved compilation problems: 
Duplicate local variable ans 
sc cannot be resolved 
Duplicate local variable redo 
sc cannot be resolved 
redo cannot be resolved to a variable 

at Application.main(Application.java:9) 

Answer 1

想你想获得水木清华这样的：

public class Application { 

    public static void main(String[] args) { 
     char redo; 
     do { 
      System.out.println("What is the command keyword to exit a loop in Java?\na. int\nb. continue\nc. break\nd. exit\nEnter your choice"); 
      Scanner scanner = new Scanner(System.in); 
      char ans = scanner.next().charAt(0); 
      if (ans == 'c') { 
       System.out.println("Correct"); 
       break; 
      } 
      else { 
       System.out.println("Wrong! Presss Y to try again."); 
       redo = scanner.next().charAt(0); 
      } 
     } 
     while (redo == 'y'); 
    } 

} 

问题的实现：

错误的变量定义

尝试重新定义ans变量导致编译错误。使用不同的变量名称。对于前：

Scanner scanner = new Scanner(System.in); 
char ans = scanner.next().charAt(0); 

，而不是这个

Scanner ans = new Scanner(System.in); 
char ans = sc.next().charAt(0); 

也许你想打破循环，如果答案是正确的

所以最好添加休息的时候ans=='c'：

if (ans == 'c') { 
    System.out.println("Correct"); 
    break; 
} 

虽然条件变量定义

定义redo可变do-while循环块，否则你会得到编译错误

Answer 2

在以下2语句中复制局部变量“ans”。重命名任何人到另一个。

Scanner ans = new Scanner(System.in); 
    char ans = sc.next().charAt(0);