How to add action listener that listens to multiple buttons

There is no this pointer in a static method. (I don't believe this code will even compile.)

You shouldn't be doing these things in a static method like main(); set things up in a constructor. I didn't compile or run this to see if it actually works, but give it a try.

public class Calc extends JFrame implements ActionListener {

    private Button button1;

    public Calc()
    {
        super();
        this.setSize(100, 100);
        this.setVisible(true);

        this.button1 = new JButton("1");
        this.button1.addActionListener(this);
        this.add(button1);
    }


    public static void main(String[] args) {

        Calc calc = new Calc();
        calc.setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
        if(e.getSource() == button1)
    }  

}

I'm amazed that nobody has mentioned using an action command. This is a pretty standard way of associating sources and listeners. Its really useful if;

• you have multiple event sources that need to do the same thing (eg if you want the use to be able to press the enter key on a text field as an alternative to clicking a button next to it)
• you don't have a ref to the component generating the event

see;

import java.awt.FlowLayout;
import java.awt.event.ActionEvent;    
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;

public class DontExtendJFrame implements ActionListener {

  private enum Actions {
    HELLO,
    GOODBYE
  }

  public static void main(String[] args) {

    DontExtendJFrame instance = new DontExtendJFrame();

    JFrame frame = new JFrame("Test");
    frame.setLayout(new FlowLayout());
    frame.setSize(200, 100);

    JButton hello = new JButton("Hello");
    hello.setActionCommand(Actions.HELLO.name());
    hello.addActionListener(instance);
    frame.add(hello);

    JButton goodbye = new JButton("Goodbye");
    goodbye.setActionCommand(Actions.GOODBYE.name());
    goodbye.addActionListener(instance);
    frame.add(goodbye);

    frame.setVisible(true);
  }

  @Override
  public void actionPerformed(ActionEvent evt) {
    if (evt.getActionCommand() == Actions.HELLO.name()) {
      JOptionPane.showMessageDialog(null, "Hello");
    } else if (evt.getActionCommand() == Actions.GOODBYE.name()) {
      JOptionPane.showMessageDialog(null, "Goodbye");
    }
  }
}