java - while 循环中的代码行在错误的时间执行

Question

程序代码:

public static void main(String[] args) throws IOException {

    System.out.print("Welcome to my guessing game! "
            + "Would you like to play (Y/N)? ");
    yesOrNoAnswer = (char)System.in.read();

    if(yesOrNoAnswer == 'Y') {
        System.out.print("\n\nGuess the number (between 1 and 10): ");
        while(AnswerIsCorrect == false) {
            guess = System.in.read();

            if(guess == correctAnswer) {
                AnswerIsCorrect = true;
            }
            else {
                System.out.print("\nYou guessed wrong! Please try again: ");
            }
        }
        System.out.print("You guessed correct! Congratulations!"
                + "\n\nPress any key to exit the program . . .");
        System.in.read();
    }
}

预期输出:

Welcome to my guessing game! Would you like to play (Y/N)? Y


Guess the number (between 1 and 10): 

实际输出:

Welcome to my guessing game! Would you like to play (Y/N)? Y


Guess the number (between 1 and 10): 
You guessed wrong! Please try again:

当我在第一个问题(你想玩吗)输入“Y”时，它会继续输出“猜猜 1 到 10 之间的数字:”这是一个很好的输出。然而，在我输入数字之前，它立即输出:“您猜错了!请重试:”

如何修复此代码以实现预期输出？

Answer 1

问题在于您对 System.in.read() 的使用。

System.in.read() 将一一读取字符并将其作为 int 返回。如果我输入 1，System.in.read() 将返回 49，因为这就是字符 1 的含义编码为。

它立即打印出您的猜测是错误的而不让您输入任何内容的原因是 System.in.read() 也会读取换行符。如果有任何未读的内容，它会读取该内容，而不是要求新的输入。您输入的 Y 之后有一个新行字符，因此它会读取该新行字符。

您应该使用扫描仪:

    Scanner scanner = new Scanner(System.in); // create a new scanner
    System.out.print("Welcome to my guessing game! "
        + "Would you like to play (Y/N)? ");
yesOrNoAnswer = scanner.nextLine().charAt(0); // reading the first character from the next line

if(yesOrNoAnswer == 'Y') {
    System.out.print("\n\nGuess the number (between 1 and 10): ");
    while(AnswerIsCorrect == false) {
        guess = Integer.parseInt(scanner.nextLine()); // get an int from the next line

        if(guess == correctAnswer) {
            AnswerIsCorrect = true;
        }
        else {
            System.out.print("\nYou guessed wrong! Please try again: ");
        }
    }
    System.out.print("You guessed correct! Congratulations!"
            + "\n\nPress any key to exit the program . . .");
    scanner.nextLine();
}

Scanner.nextLine() 将返回用户以字符串形式键入的输入，并忽略换行符。