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

public class ButtonEvent2Class {
    
    private JButton button;
    
    public ButtonEvent2Class(){
        init();
    }
    
    private void init() {
        JFrame frame = new JFrame("Button-Test");
        button = new JButton("click mich!");
        button.addActionListener(new ButtonLauscher());
        frame.add(button);
        frame.setSize(200, 200);
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
    
    class ButtonLauscher implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            if(e.getSource() == button){
                System.out.println("Button geklickt!");
            }
        }
    }
    
    public static void main(String[] args){
        SwingUtilities.invokeLater(() -> new ButtonEvent2Class());
    }
}