Step by step simple Java GUI example

step1.java

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

step2.java

class MyFrame extends JFrame {

  public MyFrame(){

  }

}

step3.java

class MyFrame extends JFrame {

  public MyFrame(){

    initComponent();
    initEvent();
  }

  private void initComponent(){

  }

  private void initEvent(){

  }
}

step4.java

class MyFrame extends JFrame {
  
  private JButton btnTutup  = new JButton("Tutup");
  private JButton btnTambah = new JButton("Tambah");

  private JTextField txtA = new JTextField();
  private JTextField txtB = new JTextField();
  private JTextField txtC = new JTextField();

  private JLabel lblA = new JLabel("A :");
  private JLabel lblB = new JLabel("B :");
  private JLabel lblC = new JLabel("C :");

  public MyFrame(){

    initComponent();
    initEvent();
  }

  private void initComponent(){

  }

  private void initEvent(){

  }
}

step5.java

  ...
  ...

  private void initComponent(){

    btnTutup.setBounds(300,130, 80,25);
    btnTambah.setBounds(300,100, 80,25);

    txtA.setBounds(100,10,100,20);
    txtB.setBounds(100,35,100,20);
    txtC.setBounds(100,65,100,20);

    lblA.setBounds(20,10,100,20);
    lblB.setBounds(20,35,100,20);
    lblC.setBounds(20,65,100,20);


    add(btnTutup);
    add(btnTambah);

    add(lblA);
    add(lblB);
    add(lblC);

    add(txtA);
    add(txtB);
    add(txtC);
  }

  ...
  ...

step6.java

  ...
  ...

  private void initEvent(){

    this.addWindowListener(new WindowAdapter() {
      public void windowClosing(WindowEvent e){
       System.exit(1);
      }
    });

    btnTutup.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        btnTutupClick(e);
      }
    });

    btnTambah.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        btnTambahClick(e);
      }
    });
  }

  ...
  ...

step7.java

  ...
  ...

  private void btnTutupClick(ActionEvent evt){
    System.exit(0);
  }
  
  private void btnTambahClick(ActionEvent evt){
    Integer x,y,z;
    try{
      x = Integer.parseInt(txtA.getText());
      y = Integer.parseInt(txtB.getText());
      z = x + y;
      txtC.setText(z.toString());

    }catch(Exception e){
      System.out.println(e);
      JOptionPane.showMessageDialog(null, 
          e.toString(),
          "Error", 
          JOptionPane.ERROR_MESSAGE);
    }
  }

  ...
  ...