Как мне центрировать мой JFrame? ⇐ JAVA

[Anonymous]

Привет, ребята, я создал небольшое приложение для входа в систему, которое подключается к моей базе данных, но у меня есть одна небольшая проблема: я понятия не имею, как центрировать фрейм, я имею в виду, когда я запускаю приложение, чтобы оно перемещалось прямо посередине экрана.
Я пробовал кое-что с этим:

Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize()


но я не уверен, где его разместить, и он неполный.
Заранее спасибо.

/*
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* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/

package mysqltryouts;

import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.Scanner;
import javax.swing.JFrame;
import javax.swing.JOptionPane;

/**
*
* @author ExtremeSwat
*/

public class login_panel extends javax.swing.JFrame {

private Connection connect = null;
private Statement statement = null;
private PreparedStatement preparedStatement = null;
private ResultSet resultSet = null;

public void readDataBase() throws Exception
{

String username = jTextField1.getText();

String password = jPasswordField1.getText();

// System.out.println(username);
// System.out.println(password);
// System.out.println("test");

//---------------------

// String databaseUsername = "";
// String databasePassword = "";

try {
// this will load the MySQL driver, each DB has its own driver

Class.forName("com.mysql.jdbc.Driver");

// setup the connection with the DB.

connect = DriverManager
.getConnection("jdbc:mysql://localhost/cards?"
+ "user=root&password=password");

//String sqlQuery = "select count(*) > 0 as match_found FROM username WHERE username = ? and password = MD5(?)";
String sqlQuery = "SELECT * FROM username WHERE username = ? and password = MD5(?)";
// String sqlQuery = "select count(*) > 0 as cnt FROM username WHERE username = ? and password = MD5(?)";

PreparedStatement pst = connect.prepareStatement( sqlQuery );
pst.setString( 1, username );
pst.setString( 2, password );

ResultSet rs = pst.executeQuery();

if( rs.next() ) {

System.out.println("You did it!");
}
else
System.out.println("Bad PW");

} catch (Exception e) {
throw e;
} finally {
close();
}

}

private void close() {
close(resultSet);
close(statement);
close(connect);
}

private void close(AutoCloseable c) throws UnsupportedOperationException {
try {
if (c != null) {
c.close();
}
} catch (Exception e) {
// don't throw now as it might leave following closables in undefined state
}

}

/**
* Creates new form login_panel
*/
public login_panel() {
initComponents();
}

/**
* This method is called from within the constructor to initialize the form.
* WARNING: Do NOT modify this code. The content of this method is always
* regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
//
private void initComponents() {

jTextField1 = new javax.swing.JTextField();
jPasswordField1 = new javax.swing.JPasswordField();
jLabel1 = new javax.swing.JLabel();
jLabel2 = new javax.swing.JLabel();
jButton1 = new javax.swing.JButton();
jButton2 = new javax.swing.JButton();
jLabel3 = new javax.swing.JLabel();

setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

jTextField1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jTextField1ActionPerformed(evt);
}
});

jPasswordField1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jPasswordField1ActionPerformed(evt);
}
});

jLabel1.setText("Username");

jLabel2.setText("Password");

jButton1.setText("Login");
jButton1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton1ActionPerformed(evt);
}
});

jButton2.setText("eXIT");
jButton2.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton2ActionPerformed(evt);
}
});

jLabel3.setFont(new java.awt.Font("Old English Text MT", 1, 36)); // NOI18N
jLabel3.setText("Login B0$$");

javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addContainerGap(66, Short.MAX_VALUE)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addComponent(jButton2)
.addContainerGap())
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addComponent(jLabel3)
.addGap(53, 53, 53))))
.addGroup(layout.createSequentialGroup()
.addGap(20, 20, 20)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jLabel1)
.addComponent(jLabel2))
.addGap(18, 18, 18)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, 92, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(18, 18, 18)
.addComponent(jButton1))
.addComponent(jPasswordField1, javax.swing.GroupLayout.PREFERRED_SIZE, 92, javax.swing.GroupLayout.PREFERRED_SIZE))
.addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(jLabel3)
.addGap(38, 38, 38)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jLabel1)
.addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(jButton1))
.addGap(4, 4, 4)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jLabel2)
.addComponent(jPasswordField1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 63, Short.MAX_VALUE)
.addComponent(jButton2))
);

pack();
}//

private void jTextField1ActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
}

private void jPasswordField1ActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
}

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {

try{

// login_panel dao = new login_panel();
//
//
// dao.readDataBase();

this.readDataBase();

}
catch(Exception e)
{
System.out.println(e.getMessage());
}

}

private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {

int dialogButton = JOptionPane.YES_NO_OPTION;

int dialogResult = JOptionPane.showConfirmDialog(null, "Exit? ", "Information",dialogButton);

if(dialogResult == JOptionPane.YES_OPTION)
{
JOptionPane.showMessageDialog(null, "Thanks for the stay","Confirm",JOptionPane.INFORMATION_MESSAGE);
System.exit(0);

}else
{
JOptionPane.showMessageDialog(null, "Remaining...","Remaining....",JOptionPane.INFORMATION_MESSAGE);

}

}

/**
* @param args the command line arguments
*/
public static void main(String args[]) {
/* Set the Nimbus look and feel */
//
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutor ... /plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(login_panel.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(login_panel.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(login_panel.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(login_panel.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//

/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new login_panel().setVisible(true);
}
});
}

// Variables declaration - do not modify
private javax.swing.JButton jButton1;
private javax.swing.JButton jButton2;
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel jLabel2;
private javax.swing.JLabel jLabel3;
private javax.swing.JPasswordField jPasswordField1;
private javax.swing.JTextField jTextField1;
// End of variables declaration
}