>>414
とりあえずこれは動いた

import java.awt.Font;
import java.util.Random;
import javax.swing.*;

public class Test
{
public static void main(String[] args)
{
SwingUtilities.invokeLater(() ->
{
Random rng = new Random();

JLabel label = new JLabel("ぬるぽ");
JFrame frame = new JFrame();
frame.getContentPane().add(label);
frame.pack();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);

Timer timer = new Timer(1000, e -> {
label.setFont(new Font(Font.MONOSPACED, 0, rng.nextInt(40) + 10));
frame.pack();
});
timer.setRepeats(true);
timer.start();
});
}
}