java - 如何从 Java 中获取用户的单个字符输入？

Question

在下面的示例中，我尝试接受来自用户的单个字符输入，但是在运行程序时，我执行了多次 do..while 循环。请在下面查看程序的结果。

如果有人能帮我解答，如何解决这个问题？

import java.io.*;



public class Main {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) throws IOException {



            char c;
           // BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
            DataInputStream in =new DataInputStream(System.in);

            // Asking the user what to do with the application
           do{ 

            System.out.println("Would you like to access your account, if yes,type 'Y' or if you want to create a new account press 'N'to exit press 'E' ");          

            byte b = in.readByte();
            c = (char) b;
            c = Character.toUpperCase(c);

            if (c=='Y'){
                System.out.println(c);
               }
            else if (c=='N') {
              System.out.println(c);
            }
            else if (c=='E'){
               System.out.println(c); 
            }
            else{
                System.out.println("Incorrect Entry, try again: "+c); 
            }

           }while (c!='E');

    }

}

输出

init:
deps-jar:
compile:
run:
Would you like to access your account, if yes,type 'Y' or if you want to create a new account press 'N'to exit press 'E' 
asdfgaf
Incorrect Entry, try again: A
Would you like to access your account, if yes,type 'Y' or if you want to create a new account press 'N'to exit press 'E' 
Incorrect Entry, try again: S
Would you like to access your account, if yes,type 'Y' or if you want to create a new account press 'N'to exit press 'E' 
Incorrect Entry, try again: D
Would you like to access your account, if yes,type 'Y' or if you want to create a new account press 'N'to exit press 'E' 
Incorrect Entry, try again: F
Would you like to access your account, if yes,type 'Y' or if you want to create a new account press 'N'to exit press 'E' 
Incorrect Entry, try again: G
Would you like to access your account, if yes,type 'Y' or if you want to create a new account press 'N'to exit press 'E' 
Incorrect Entry, try again: A
Would you like to access your account, if yes,type 'Y' or if you want to create a new account press 'N'to exit press 'E' 
Incorrect Entry, try again: F
Would you like to access your account, if yes,type 'Y' or if you want to create a new account press 'N'to exit press 'E' 
Incorrect Entry, try again: 

Would you like to access your account, if yes,type 'Y' or if you want to create a new account press 'N'to exit press 'E' 

Answer 1

使用 DataInputStream 可能不是处理您的情况的最佳方式。

DataInputStream 缓冲您键入的输入，这就是为什么您会收到不需要的带有循环的冗长消息。

尝试改用扫描仪。这是扫描仪的示例:

Scanner objScanner = new Scanner(System.in);
char c = objScanner.next().charAt(0);
System.out.println(c);