如何在 java 中执行字母数字字符串

Question

当我将 CS1001 作为输入时，输出必须显示有效消息。除此之外，每个输入都必须无效。我不明白我要申请什么逻辑？

import java.util.Scanner;

public class EmployeeInfo {
    private static final String CSXXX = "";

    public void empCheck(String empId) throws InvalidEmployeeException {
        if (!CSXXX.equals(empId))
            throw new InvalidEmployeeException("Employee ID inValid");
        else
            System.out.println("Employee ID is Valid");

    }

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        System.out.println("Main Starts....");
        EmployeeInfo ei = new EmployeeInfo();
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter Employee ID");
        String w = sc.nextLine();
        try {
            ei.empCheck(w);
        } catch (InvalidEmployeeException iee) {
            System.out.println(iee);
        }
        System.out.println("Main End...");
    }
}

InvalidEmployeeException.java

public class InvalidEmployeeException extends Exception {
    public InvalidEmployeeException(String s) {
        // TODO Auto-generated constructor stub
        super(s);
    }
}

Answer 1

 import java.util.Scanner;

public class EmployeeInfo {

    String Str = "CS";

    public void empCheck(String empId) throws InvalidEmployeeException {

        if (!empId.startsWith(Str)) 

            // if (!CSXXX.equals(empId))
            throw new InvalidEmployeeException("Employee ID is inValid");
        else
            System.out.println("Employee ID is Valid");

    }

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        System.out.println("Main Starts....");
        EmployeeInfo ei = new EmployeeInfo();
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter Employee ID");
        String w = sc.nextLine();

        try {
            ei.empCheck(w);
        } catch (InvalidEmployeeException iee) {
            System.out.println(iee);
        }
        System.out.println("Main End...");
    }

}

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