java - 如何测试循环中是否有多个字母

Question

我的作业说明如下

如果学生输入的成绩不是一个字母，请使用 System.out.println() 方法告诉学生重试。

这是我正在使用的代码

import java.io.IOException;
import java.util.Scanner;
public class MyGradeLoops {

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

    for (int x = 1; x <= 5; x++) {

        System.out.println("Please enter Your Class Grades");
        String A;
        char B;
        A = in.next();
        System.out.println("Thank You");
        if (**TRYING TO TEST FOR MORE THAN ONE LETTER**) {
            System.out.println("Only One Letter At A Time");
        }
    }
    System.out.println("Keep Up The Good Work")
  }
}

感谢任何帮助

Answer 1

import java.io.IOException;

import java.util.Scanner;

public class MyGradeLoops {
public static void main(String[] args) throws IOException {
    Scanner in = new Scanner(System.in);
    for (int x = 1; x <= 5; x++) {
        System.out.println("Please enter Your Class Grades");
        String A;
        char B;
        A = in.next();
        System.out.println("Thank You");
        if (A.length() != 1) {
            System.out.println("Only One Letter At A Time");
        }
    }
    System.out.println("Keep Up The Good Work");
}
}