import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Container;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.border.Border;
import javax.swing.border.LineBorder;
public class MainClass {
public static void main(final String args[]) {
JFrame frame = new JFrame("Line Borders");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Border roundedBorder = new LineBorder(Color.BLACK, 12, true);
JButton roundedButton = new JButton("Rounded 12 Pixel");
roundedButton.setBorder(roundedBorder);
Container contentPane = frame.getContentPane();
contentPane.add(roundedButton, BorderLayout.SOUTH);
frame.pack();
frame.setSize(300, frame.getHeight());
frame.setVisible(true);
}
}