TypewriterJFrame.java

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

public class TypewriterJFrame extends JFrame implements ActionListener {

    /** Application:    TypewriterJFrame.java by Chris Clarke, 07 September 2016.
      * Purpose:    Example of text "typed" automatically in a JFrame TextArea.
      **/


    Panel       userControls;
    TextArea    ta1;
    Button      btnSet;
    boolean     paint=false;
    final String    txt = "Entering the Dragon's lair,\nI watched as ..."; // or put own text here

    TypewriterJFrame() {
        setTitle("Typewriter by Chris Clarke");
        setLayout(new BorderLayout());
        userControls = new Panel();
        ta1=new TextArea("", 2, 35);
        userControls.add(ta1);

        btnSet=new Button("Press me!");
        btnSet.addActionListener(this);
        userControls.add(btnSet);

        add("North",userControls);
    }

    public static void main(String[] args) {
        TypewriterJFrame frame = new TypewriterJFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        // Set to a reasonable size.
        frame.setSize(1024, 768);
        frame.setVisible(true);
    }

    public void paint(Graphics g) {
        if (!paint) {
            g.setColor(Color.WHITE);
            g.fillRect(0,0,1024,768);
            return;
        }
        String output="";
        for (int c=0; c<txt.length(); c++) {
            output += txt.charAt(c);
            ta1.setText(output);
            for (long num=0; num<50000000; num++); // try other values
        }
    }

    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == btnSet) {
            paint=true;
            repaint();
        }
    }
}