什麼在我的代碼是錯誤的（Java字符輸入的初學者）

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'); 
} 

}

我剛開始學習Java，可以請你告訴我，什麼是錯在我的代碼，以及如何改進呢？謝謝

這是我收到的錯誤。

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

想你想獲得水木清華這樣的：

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'); 
    } 

} 

問題的實現：

錯誤的變量定義

嘗試重新定義ans變量導致編譯錯誤。使用不同的變量名稱。對於前：

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

，而不是這個

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

也許你想打破循環，如果答案是正確的

所以最好添加休息的時候ans=='c'：

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

雖然條件變量定義

定義redo可變do-while循環塊，否則你會得到編譯錯誤

Answer 2

在以下2語句中複製局部變量「ans」。重命名任何人到另一個。

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