Java lat-4

//Nama Program:lat4.java

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class lat4 extends JFrame implements ActionListener{

JLabel jLabel1=new JLabel();
JTextField jText=new JTextField();
JButton jButton1=new JButton();

public static void main(String args[]){
  lat4 windowku=new lat4();
  windowku.setSize(400,250); 
  Dimension screen =Toolkit.getDefaultToolkit().getScreenSize();
  int lebar=(screen.width-windowku.getSize().width)/2;
  int tinggi=(screen.height-windowku.getSize().height)/2;
  windowku.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  windowku.setLocation(lebar,tinggi);  
  windowku.setVisible(true); 
  windowku.setResizable(false);  
}
public lat4(){
  this.getContentPane().setLayout(null);
  jLabel1.setFont(new java.awt.Font("Comic Sans MS",1,14)); //Jenis Font,Ketebalan,Size)
  jLabel1.setText("Menghitung Jumlah Karakter.....!"); 
  jLabel1.setBounds(new Rectangle(50,0,300,25)); //Kolom, baris, Lebar, Tinggi
  jText.setBounds(new Rectangle(70,25,200,25));
  jButton1.setBounds(new Rectangle(126,87,65,20));
  jButton1.setText("OK");
  jButton1.addActionListener(this);
  this.getContentPane().add(jLabel1,null);
  this.getContentPane().add(jText,null);
  this.getContentPane().add(jButton1,null);

  try {
  this.setTitle("Sunardi,S.Kom");
}
  catch(Exception e) {
e.printStackTrace();
}
}
public void actionPerformed(ActionEvent e) {
hitungKarakter();
}

public void hitungKarakter() {
int jumlahKarakter=jText.getText().length();
  JOptionPane.showMessageDialog(null,"Jumlah karakter adalah"+jumlahKarakter);
  jText.setText("");
}
}