Question

这是我的代码：

public class Main extends JFrame{

static int NoOfUsers;
static String[][] Accounts = new String[NoOfUsers][2];

public static void main(String[] args){
    Login();
}

private static void Login() {
    final String FileName = "F:/TextFiles/loginaccs.txt";
    try {
        BufferedReader file = new BufferedReader(new InputStreamReader(new FileInputStream(FileName)));
        int NoOfUsersL = Integer.parseInt(file.readLine());
        String[][] Accounts = new String[NoOfUsersL][2];
        NoOfUsers = NoOfUsersL;
        for (int i=0; i<NoOfUsersL; i++) {
            Accounts[i][0] = file.readLine();
            Accounts[i][1] = file.readLine();
        }
        for (int i=0; i<NoOfUsersL; i++) {
            System.out.println(Accounts[i][0]);
            System.out.println(Accounts[i][1]);
        }
        file.close();

    } catch (IOException e) {
        System.out.println("ERROR: unable to read file.");
        e.printStackTrace();   
    }    

    String username = null;
    String password = null;
    JTextField usernamejtf = new JTextField(username);
    JPasswordField passwordjtf = new JPasswordField(password);
    String[] buttons = {"Login", "Create new account"};
    Object[] InputDialog = {
            "Username: ", usernamejtf, "Password: ", passwordjtf
    };

    do {

    int option = JOptionPane.showOptionDialog(null, 
            InputDialog, 
            "Login", 
            JOptionPane.DEFAULT_OPTION, 
            JOptionPane.PLAIN_MESSAGE, 
            null, 
            buttons, 
            buttons[0]);
    System.out.println(option); //Check

    if (option == JOptionPane.CLOSED_OPTION ) {
        return;
    }
    else if (option == 0) {
        if (CheckAccount(username,password)) {
            System.out.println("Logged in");
        } else {
            System.out.println("Wrong Password/Username");
        }
    } else if (option == 1) {
        System.out.println("Create Account.");
        }

    } while (!(CheckAccount(username,password)));
}


private static boolean CheckAccount(String username, String password) {
    for (int i=0; i>NoOfUsers; i++) {
        if ((username == Accounts[i][0]) && (password == Accounts[i][1])) {
            return true; 
        }
    }
    return false;
}

}

在＆＃34; main＆＃34;中，我调用了Login（）方法，Eclipse强迫我将单词＆＃34; static＆＃34;在方法名称前面。
无论如何，我可以修改程序，以便该行可以写为： private void Login（）{...}; private boolean CheckAccount（...）{...}等？

[额外问题：由于＆＃34;静态＆＃34;这个词，我不能把“＆＃34; public＆＃34;在String [] [] Accounts = new String [NoOfUsersL] [2];
之前这使得CheckAccount无法访问Accounts数组。如何修改程序以解决此问题。]
每个人都提前。

Answer 1

静态方法可以是调用静态方法（没有实例）所以要调用实例方法首先创建它并从实例调用exampled，如下所示

   private void textBox22_TextChanged(object sender, EventArgs e)
    {
        String path = "Data Source=LOCALHOST; Initial Catalog= sadd; username=root; password=''";
        MySqlConnection sqlconn = new MySqlConnection(path); //communicator //constructors
        MySqlCommand sqlcomm = new MySqlCommand();
        MySqlDataReader sqldr;
        sqlconn.Open();
        sqlcomm.Connection = sqlconn;
        sqlcomm.CommandType = CommandType.Text;
        sqlcomm.CommandText = "Select * from approvedrecords where VoucherNumber=" + textBox22.Text + "";

        sqldr = sqlcomm.ExecuteReader();
        sqldr.Read();

        if (sqldr.HasRows)
        {
            textBox26.Text = sqldr[0].ToString();

        }
        sqlconn.Close();


        if (textBox22.Text == textBox26.Text)
        {

            String path8 = "Data Source=LOCALHOST; Initial Catalog= sadd; username=root; password=''";
            MySqlConnection sqlcon = new MySqlConnection(path8); //communicator //constructors

            string query = "select * from approvedrecords where VoucherNumber = " + textBox22.Text + " ";
            MySqlCommand cmd = new MySqlCommand(query, sqlcon);
            MySqlDataReader dbr;


            sqlcon.Open();
            dbr = cmd.ExecuteReader();
            while (dbr.Read())
            {

                string a = (string)dbr["CheckNumber"].ToString();
                string b = (string)dbr["DateCreated"];
                string c = (string)dbr["Status"];
                string d = (string)dbr["PayeesName"];
                string f = (string)dbr["Amount"].ToString();
                string g = (string)dbr["DatePrinted"];
                string h = (string)dbr["Particulars"];
                string i = (string)dbr["Prepared_by"];
                string j = (string)dbr["Payment_received_by"];

                textBox21.Text = a;
                textBox23.Text = b;
                textBox28.Text = c;
                textBox20.Text = d;
                textBox19.Text = f;
                textBox27.Text = g;
                textBox18.Text = h;
                textBox16.Text = i;
                textBox17.Text = j;

            }
        }
        else
        {
            MessageBox.Show("ID doesn't exist!");
        }

Answer 2

执行new Main().login();

您应遵循java命名约定，变量和方法名称应以小写字母开头。

Answer 3

使用：

public static void main(String[] args){
    Main main = new Main();
    main.login();
}

Answer 4

为了删除静态限定符，必须使所有方法和变量实例变量和方法。然后，您可以实例化JFrame对象并调用login()。

我还根据Java官方约定将方法/变量名称转换为mixedCase。我认为你开始用VB或C＃编程？

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;

import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPasswordField;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;

public class Main extends JFrame {
    private static final long serialVersionUID = -105943237549003486L;

    private int numOfUsers;
    private String[][] accounts;

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                Main m = new Main();

                m.login("F:/TextFiles/loginaccs.txt");
            }
        });
    }

    // Constructor, set up instance values here.
    public Main() {
        super();
    }

    private void login(final String fileName) {
        try {
            BufferedReader file = new BufferedReader(new InputStreamReader(new FileInputStream(fileName)));

            numOfUsers = Integer.parseInt(file.readLine());
            accounts = new String[numOfUsers][2];

            for (int i = 0; i < numOfUsers; i++) {
                accounts[i][0] = file.readLine();
                accounts[i][1] = file.readLine();
            }

            for (int i = 0; i < numOfUsers; i++) {
                System.out.println(accounts[i][0]);
                System.out.println(accounts[i][1]);
            }

            file.close();

        } catch (IOException e) {
            System.out.println("ERROR: unable to read file.");
            e.printStackTrace();
        }

        String username = null;
        String password = null;
        JTextField usernamejtf = new JTextField(username);
        JPasswordField passwordjtf = new JPasswordField(password);
        String[] buttons = { "Login", "Create new account" };
        Object[] InputDialog = { "Username: ", usernamejtf, "Password: ", passwordjtf };

        do {
            int option = JOptionPane.showOptionDialog(null, InputDialog, "Login", JOptionPane.DEFAULT_OPTION,
                    JOptionPane.PLAIN_MESSAGE, null, buttons, buttons[0]);
            System.out.println(option); // Check

            if (option == JOptionPane.CLOSED_OPTION) {
                return;
            } else if (option == 0) {
                if (checkAccount(username, password)) {
                    System.out.println("Logged in");
                } else {
                    System.out.println("Wrong Password/Username");
                }
            } else if (option == 1) {
                System.out.println("Create Account.");
            }

        } while (!(checkAccount(username, password)));
    }

    private boolean checkAccount(String username, String password) {
        for (int i = 0; i > numOfUsers; i++) {
            if (username == accounts[i][0] && password == accounts[i][1]) {
                return true;
            }
        }

        return false;
    }
}

如何摆脱＆＃34;静态＆＃34;？

4 个答案: