java - 有没有办法将文件中的类实现到新文件中？

Question

我有一个非常基本的登录程序:

import javax.swing.JOptionPane.*;
import java.lang.Math.*;
import java.lang.System.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
import javax.swing.JFrame;

public class UserLog extends JFrame  

{

public static void main(String[]Args) throws InterruptedException 
    {
    boolean isValid=false;
    while(!isValid)
        {
    // Components related to "login" field    
    JLabel label_loginname = new JLabel("Enter your login name:");    
    JTextField loginname = new JTextField(15);    
    // loginname.setText("EnterLoginNameHere"); 
    // Pre-set some text    
    // Components related to "password" field    
    JLabel label_password = new JLabel("Enter your password:");    
    JPasswordField password = new JPasswordField();    
    // password.setEchoChar('@'); 
    // Sets @ as masking character    
    // password.setEchoChar('\000'); 
    // Turns off masking    
    JCheckBox rememberCB = new JCheckBox("Remember me");

    Object[] array = {label_loginname,
    loginname,                       
    label_password,                       
    password,                       
    rememberCB};
    Object[] options = {"Login", "Cancel"};
    int res = JOptionPane.showOptionDialog(null,
                                            array,
                                            "Login",
                                            JOptionPane.YES_NO_OPTION,
                                            JOptionPane.QUESTION_MESSAGE,
                                            null,     //do not use a custom Icon
                                            options,  //the titles of buttons
                                            options[0]); //default button title

    // User hit Login    
    if (res == 0) 
        { 
            System.out.println( "Login" ); 
        }    
    // User hit CANCEL    
    if (res == 1) 
        { 
            System.out.println( "Canceled" ); 
        }    
    // User closed the window without hitting any button    
    if (res == JOptionPane.CLOSED_OPTION) 
        { 
            System.out.println( "CLOSED_OPTION" ); 
        }


    // Output data in "login" field, if any    
    String newloginname = loginname.getText();    
    String newpassword = new String(password.getPassword());    
    if (newloginname.equalsIgnoreCase("Cody_Coulter") && newpassword.equals("cheche1"))
        {
            System.out.println("Login Successful!");
            boolean selectedCB = rememberCB.isSelected();    
            System.out.println( "selectedCB: " + selectedCB );
            Thread.sleep(3000);
            Object[] array1= {"It's about time to choose"};
            Object[] options1= {"Leave", "Keep Going"};
            int res1 = JOptionPane.showOptionDialog(null,
                                            array1,
                                            "There",
                                            JOptionPane.YES_NO_OPTION,
                                            JOptionPane.QUESTION_MESSAGE,
                                            null,     //do not use a custom Icon
                                            options1,  //the titles of buttons
                                            options1[0]); //default button title
            if(res1==1)
                {
                    Object[] options2 = {"Answers for Algebra", 
                                         "Answers for APUSH",
                                         "Answers for Computer Science"};
                    Object[] array2={"Pick Your Poison:"};
                    int res2= JOptionPane.showOptionDialog(null,
                                                array2,
                                                "This",
                                                JOptionPane.YES_NO_OPTION,
                                                JOptionPane.QUESTION_MESSAGE,
                                                null,     //do not use a custom Icon
                                                options2,  //the titles of buttons
                                                options2[0]); //default button title
                    if (res2 == 0) 
                    { 
                        JOptionPane.showMessageDialog(null, "Nigguh you a cheatuh" ); 
                    }    
                    else
                    if (res2 == 1) 
                    { 
                        JOptionPane.showMessageDialog(null, "Nigguh, who's dumb enough to need to cheat in APUSH" ); 
                    }
                    else
                    if (res2 == 2) 
                    { 
                        JOptionPane.showMessageDialog(null, "Nigguh, you dumb" ); 
                    }     

                    String name1 = JOptionPane.showInputDialog(null,
                                                        "What is your name?");
                    int length = 0;
                    length = newpassword.length();
                    String Pass = "*";
                    newpassword =newpassword.replaceAll(".","*");
                    System.out.println("Username: "+newloginname+"\nPassword: "+
                                        newpassword+"\nName: "+name1);
                }

        }
    else {
            JOptionPane.showMessageDialog(null,"Wrong Username or Password!");
            isValid=false;
         }

        }
    // Output data in "password" field, if any    
    // Output state of "remember me" check box    

    }

}

我想做的是创建另一个程序，例如文件共享、文件访问，甚至是基本游戏，但能够实现此登录，当然是为了登录。有没有一种方法可以实现此代码，而无需将其作为该文件中的单独类复制并粘贴到另一个代码中？ 示例:

public class NewGame{
     public static void main(String[] args)
     {
         new UserLog();
     }

当然，这在语法上可能不正确，但这就是要点。

谢谢，如果我需要重新措辞或编辑问题/格式，请告诉我! :)

编辑 将当前的 main 方法设为常规公共(public)类，并从新的公共(public)类中调用后，通过新的 main

public class gameLogin
{
public static void main(String[]args) 
{ 
    userLogin(); 
} 
public class userLogin() 
{ 
   // current code, evidently seen in the current main  
}
// rest of code

因此，为了引用原始文件 userLog，我必须(在新文件:gameLogin 中)使用 用户日志()；

或者使用会更好

userLog.userLogin("Munkeeface", "password");

Answer 1

最简单的方法是将所有代码从 main 移至静态实用程序类函数中，然后从其他类 main 调用该函数。例如:

public class LoginToWebsiteUtil  {
   public static final void login(String username, String password, ...)  {
      //CODE GOES HERE
   }
}

并将其用于:

public class LoginToMyWebsite  {
   public static final void main(String[] ignored)  {
      LoginToWebsiteUtil.login("myname", "password", ...)
   }
}          

唯一棘手的事情是回答这个问题:“什么变量保存状态？”这些变量必须在实用程序类中声明为静态类字段。这是因为，一旦函数结束，所有状态(例如登录连接)都将终止。为了保持它(“保持其状态”)，这些状态变量需要具有比函数的生命周期更大的范围。

例如，而不是

public class LoginToWebsiteUtil  {
   public static final void login(String username, String password, ...)  {
      Connection conn = getConnectionFromLogin(username, password);

      //and so on...

必须是

public class LoginToWebsiteUtil  {
   private static Connection conn = null;
   public static final void login(String username, String password, ...)  {
      conn = getConnectionFromLogin(username, password);

      //and so on...

或者，您可以将原始 main 函数中的所有代码放入新类的构造函数中，例如

public class UserLogin  {
   private static Connection conn = null;
   public UserLog(String username, String password, ...)  {
      conn = getConnectionFromLogin(username, password);
      //CODE HERE
   }
}

但是，正如您所看到的，您仍然有“什么保持状态？”问题。

(这是一个好问题。听起来这个登录代码将来对您可能有用。)