import java.awt.BorderLayout;
import javax.swing.JButton;
import javax.swing.JWindow;
public class Main {
public static void main(String[] argv) throws Exception {
JWindow window = new JWindow();
JButton component = new JButton("asdf");
// Add component to the window
window.getContentPane().add(component, BorderLayout.CENTER);
// Set initial size
window.setSize(300, 300);
// Show the window
window.setVisible(true);
}
}