基本Java错误

好的，我的代码如下

  //Variables
  Scanner keyboard = new Scanner(System.in);
  String userGuess = keyboard.nextLine().toUpperCase();
  final String correctAnswer = "RBR";

  //Mastermind program
  //Welcome message
  System.out.println("\nHello " +/*username*/" and welcome to Mastermind!\n");
  System.out.println("##########################################################################\n");
  System.out.println("In this game you have 3 guesses to guess the order of a sequence of letters," +
        "\nthe sequence will consist of the letters R and/or B, in a random order" +
        "\nand you have to guess the order that they are in." +
        "\nYou will be awarded points depending on how many guesses it takes you to" +
        "\nguess the sequence and how many letters you get correct.\n");
  System.out.println("##########################################################################\n");


  //Game start
  System.out.println("Please enter your first guess: " + userGuess);
  if(userGuess.equals(correctAnswer)){
     System.out.println("Congratulations you got it in one go!");
  }
  else{
     System.out.println("Sorry try again");
  }

---

我只是想知道为什么当我运行它时，我必须立即输入我的猜测，而没有它运行欢迎消息，它只在我按enter键后运行，然后告诉我我是正确的还是错误的，认为这与我有关。下一行但我不确定？

您需要移动代码：

String userGuess = keyboard.nextLine().toUpperCase();

在这样的欢迎信息之后：

//Game start
 System.out.println("Please enter your first guess: " + userGuess);
 Scanner keyboard = new Scanner(System.in);
 String userGuess = keyboard.nextLine().toUpperCase();

把它移到这里来

//Game start
 System.out.println("Please enter your first guess:");
 Scanner keyboard = new Scanner(System.in);
 String userGuess = keyboard.nextLine().toUpperCase();
 System.out.println("Your guess is: " + userGuess);

---

这是因为您有以下内容：String userGuess=keyboard.nextLine（）.toUpperCase（）；在收到你的欢迎信之前，非常感谢！所以只需使用keyboard.nextLine（）；在实际的节目中？是的。nextLine（）需要您按enter键才能继续。只要这一行在欢迎词之前，就必须首先处理这个问题