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


public class Hello extends JPanel {	
	public Hello() {
		setPreferredSize(new Dimension(250, 50));
	}
	
	@Override
	public void paintComponent(Graphics g) {
		super.paintComponent(g);
		g.drawString("HELLO WORLD!", 50, 25);
	}

	public static void main(String[] args) {
		SwingUtilities.invokeLater(() -> {
			JFrame frame = new JFrame("こんにちは"); // タイトル部分
			frame.add(new Hello());
			frame.pack();
			frame.setVisible(true);
			frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		});
	}
}