import java.applet.*;

import java.awt.*;

import java.awt.event.*;

public class ClickButton extends Applet implements ActionListener{

	// declare a textfield and Button

	TextField text1;

	Button button1;

	// initialise the applet

	public void init(){

		// set the textfield to 30 characters

		text1 = new TextField(30);

		// add the textfield to the applet

		add(text1);

		// initialise button and set its label

		button1 = new Button(" click me");

		// add button to the applet

		add(button1);

		// set the actionlistener to the button

		button1.addActionListener(this);

	}

	// methods needed for actionlistener Interface

	public void actionPerformed(ActionEvent e){

		// declare and initialise a string to be shown

		String message = " You clicked the button. woo hoo";

		// if the source of the action is the button

		// ie if the button is clicked

		if(e.getSource() == button1){

			// set the text of the textfield to our message

			text1.setText(message);

		}

	}

}

And here is the html code to run it, just as a reminder.