Display.java

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextArea;

public class Foo{

    public static void main(String[] args) {

        JFrame f = new JFrame("A JFrame");
        f.setSize(250, 250);
        f.setLocation(300,200);
        final JTextArea textArea = new JTextArea(10, 40);
        f.getContentPane().add(BorderLayout.CENTER, textArea);
        final JButton button = new JButton("Click Me");
        f.getContentPane().add(BorderLayout.SOUTH, button);
        button.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                textArea.append("Button was clicked\n");

            }
        };

        f.setVisible(true);

    }

}