要求输入用户名并将其打印出来的 Java 程序 - 出现错误消息

Question

我有一个程序会询问用户的姓名并将其打印出来。它可以很好地完成该部分，但是当用户将提示留空并按“Enter”时，它当前存在不打印正确错误消息的问题。

代码：

  //Get User Input
  Scanner sc = new Scanner(System.in);
  System.out.println("What is your name?");

  while (sc.hasNext()) {
     //User Input Variable
     String name = sc.nextLine();
     if (name == null || name.trim().isEmpty()) {
        //Error for empty input, keep asking for valid input
        System.out.print("Please, what is your name?\n");
        sc.next();
     } else {
        //Print name
        System.out.println("Hello " + name + "!");
        break;
     }//End of conditional
  }//End of while loop

当前输出：

What is your name?
<blank space for input>
<Empty Space where error message should be>

理想的输出：

What is your name?
<blank space>
Please, what is your name?

怎么了？

Answer 1

您唯一需要更改的是while 语句中的条件。 请使用sc.hasNextLine() insted 或sc.hasNext()。然后你会得到想要的输出。这是工作解决方案：

    // Get User Input
    Scanner sc = new Scanner(System.in);
    System.out.println("What is your name?");

    while (sc.hasNextLine()) { // here is the difference in the code
        // User Input Variable
        String name = sc.nextLine();
        if (name == null || name.trim().isEmpty()) {
            // Error for empty input, keep asking for valid input
            System.out.print("Please, what is your name?\n");
            sc.hasNextLine(); // here is the difference in the code
        } else {
            // Print name
            System.out.println("Hello " + name + "!");
            break;
        } // End of conditional
    } // End of while loop