如何在Java中从用户获取单字符输入？

Question

在下面的例子中，我试图接受用户的单字符输入，但是当运行程序时，我得到do...而循环执行多次。请参阅下面程序的结果。

如果有人能帮我找到答案，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');

    }

}

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

DataInputStream（InputStream）基本上是一个二进制结构。如果你想读取文本数据（例如从控制台），你应该使用读卡器。在源代码中有一个注释掉的BufferedReader。最好使用相同的代码，而不是DataInputStream。你可以做如下的事情，

BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
String input = in.readLine();

或者您可以使用DataInputStream.readLine（），但不建议使用它是有原因的。它也建议使用BufferedReader.readLine（）。

你可以选择其他选项，比如扫描仪。

Answer 2

使用系统。在里面read（）而不是DataInputStream。

Answer 3

使用数据输入流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带有循环的不需要的长消息。

试着改用扫描仪。以下是扫描仪的一个示例：

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