我的Java代碼由于錯誤而沒有運行，我該如何修復它以運行

我得到的錯誤是：錯誤：無法找到或加載主類 Main 原因：java.lang.ClassNotFoundException：Main

我是 Java 新手，不明白在這種情況下要做什么或如何修復此代碼以運行

由于錯誤描述，我認為這與類有關，但我不確定

import java.util.Scanner;
import java.util.regex.*;

class Login{
    String user;
    String password;
    String firstName;
    String lastName;

    boolean checkUserName(String user){
        if(user.length()>5 || user.indexOf('_')==-1){
            return false;
        }
        else{
            return true;
        }
    }

    boolean checkPasswordComplexity(String password){
        String regex = "^(?=.*[0-9])"
                         "(?=.*[a-z])(?=.*[A-Z])"
                         "(?=.*[@#$%^& =])"
                         "(?=\\S $).{8,20}$";
        Pattern p = Pattern.compile(regex);
        Matcher m = p.matcher(password);
        return m.matches();
    }

    boolean loginUser(String user,String password){
        if(user.equals(this.user) && password.equals(this.password)){
            return true;
        }
        else{
            return false;
        }
    }

    String returnLoginStatus(String user,String password){
        if(loginUser(user, password)){
            return "Welcome " firstName lastName " it is greater to see you again.";
        }
        else{
            return "Username or passoword incorrect, please try again.";
        }
    }

    void registerUser(String firstName,String lastName,String user,String password){

        if(checkUserName(user)){
            this.user = user;
            System.out.println("Username successfully Captured");
        }
        else{
            System.out.println("Username is not correctly formatted, please ensure that your username contains an underscore and is no more than 5 characters long.");
        }
       if(checkPasswordComplexity(password)){
           this.password = password;
            System.out.println("Password successfully captured");
        }
        else{
            System.out.println("Password is not correctly formatted, please ensure that the passoword contains atleast 8 characters, a capital letter, a number and a special character.");
        }
        if(checkUserName(user) && checkPasswordComplexity(password)){
            this.firstName = firstName;
            this.lastName = lastName;
            System.out.println(returnLoginStatus(user, password));
        }
    }
}

class Registration{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        
        System.out.print("Enter the username:");
        String user = sc.nextLine();
        System.out.print("Enter the password:");
        String password = sc.nextLine();
        System.out.print("Enter your First Name:");
        String firstName = sc.nextLine();
        System.out.print("Enter Your Last Name:");
        String lastName = sc.nextLine();
        sc.close();
        Login user1 = new Login();
        user1.registerUser(firstName, lastName, user, password);

    }
   
    
}

uj5u.com熱心網友回復：

每當在該網站上編譯 Java 代碼時，該網站的編譯器都會查找名為“Main”的類以開始執行。一旦其編譯器找到該類，它就會呼叫任何具有public static void main(String[] args). 在您的情況下，沒有名為“Main”的類，因此編譯器不知道從哪里開始運行程式。一個簡單的解決方法是將類名“Registration”更改為“Main”。

標籤：爪哇 班级 哎呀 方法

上一篇：如何使用Python類列印數獨板？

下一篇：使用狀態模式了解物件的狀態