解决方案

下面是使用这个布尔变量更新的代码，就像前面提到的注解部分一样。
但是您还必须考虑添加try/catch/finally块，然后在finally块部分关闭扫描仪（finally将始终被调用）
因为你现在循环直到你有正确的猜测，你必须在循环之外创建随机变量，否则它会在每次迭代中创建一个新的随机字符。
另外，我去掉了这些控制循环，实际上使用char的一个很大的好处是可以将那里的ascii值与其他char进行比较。
在这里，我们只是比较大写字符，我们可以直接比较这些字符彼此 enteredLetter > randomLetter 例如。
例子：

enteredLetter = 'A';
randomLetter = 'D';
enteredLetter > randomLetter

此比较将检查ascii值a=65>d=69，以便a不大于d，并转到下一个条件。
此外，您还应该检查带有字符的有效输入，方法应该是character isleter（）类的静态方法。也不要将输入作为字符串，而是直接将输入作为字符 char myLetter = scan.next().charAt(0); ```
package hall;

import java.util.Scanner;

public class GuessingGame {

public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    Boolean isGuessed = false;
    char[] characters = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q',
            'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' };
    char randomLetter = characters[(int) (Math.random() * 26)];

    while (!isGuessed) {

        System.out.println("Guess the Letter");
        char myLetter = scan.next().charAt(0);
        if(!(Character.isLetter(myLetter))) {
            System.out.println("Invalid Input Try Again:");
        }else {

        char enteredLetter = Character.toUpperCase(myLetter);

        if (enteredLetter == randomLetter) {
            System.out.println("Correct Guess");
            System.out.println("The letter is:" + randomLetter);
            isGuessed = true;
        }

        else if (enteredLetter > randomLetter) {
            System.out.println("Incorrect Guess");
            System.out.println("The letter is too high");

        }

        else if (enteredLetter < randomLetter) {
            System.out.println(enteredLetter);
            System.out.println("Incorrect Guess");
            System.out.println("The letter is too low");

        }

        }
    }

}

}

这就是你想要的：

import java.util.Scanner;

public class GuessTheLetter {

    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);

        System.out.println("Guess the Letter:-\n");

        char randomLetter = (char) (Math.random() * 26 + 65); // logic to generate random letter

        char enteredLetter = 0; // initializing variable to store entered letter

        while (true) {// infinite loop till correct guess
            System.out.print("\nEnter your Guess : ");
            enteredLetter = Character.toUpperCase(scan.next().charAt(0)); // emter letter
            if (enteredLetter == randomLetter) {
                System.out.println("Correct Guess");
                System.out.println("The letter is:" + randomLetter);
                break;// exit loop if correct letter is guessed
            } else if (enteredLetter > randomLetter) // we can directly compare char like int
            {
                System.out.println("Incorrect Guess");
                System.out.println("The letter entered is too high");
            }

            else if (enteredLetter < randomLetter) // we can directly compare char like int
            {
                System.out.println("Incorrect Guess");
                System.out.println("The letter entered is too low");
            }

        }
        scan.close();
    }

}

解释在节目的评论里！