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

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.Timer;

public class Main {

  public static void main(String[] args) {
    JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setLayout(new BorderLayout());
    frame.add(new TestPane());
    frame.setSize(100, 100);
    frame.setVisible(true);
  }
}
class TestPane extends JPanel {
  String text = "Hello";
  JLabel label;
  int charIndex = 0;

  public TestPane() {
    setLayout(new GridBagLayout());
    label = new JLabel();
    add(label);
    Timer timer = new Timer(1000, new ActionListener() {
      @Override
      public void actionPerformed(ActionEvent e) {
        String labelText = label.getText();
        labelText += text.charAt(charIndex);
        label.setText(labelText);
        charIndex++;
        if (charIndex >= text.length()) {
          ((Timer) e.getSource()).stop();
        }
      }
    });
    timer.start();
  }
}