How can I specify that a border should have a certain length on a side?

Question

how to customize a border so that length can be specified?
(I know that you can use createMatteBorder() to specify which sides should have a border. But this is different - how do you specify the length on a side).
for example, here is one side: --- is the side and ==== is the border
===========
how do I implement it?
I am stumped.
thanks,
Anil

Answer 1

BorderFactory does dispense some static instances depending on the type of
border being created. But you'll need to subclass MatteBorder to customize it;
I don't think you'll be able to do it via BorderFactory. You can either override
the paintBorder method to not paint the entire top part of the border or paint
over it; the latter approach is taken below:
import java.awt.*;
import javax.swing.border.MatteBorder;
import javax.swing.*;
public class PartiallyPaintedBorder extends MatteBorder {
     private final static int MARGIN = 15;
     public PartiallyPaintedBorder( int top, int left, int bottom, int right, Icon tileIcon ) {
          super( top, left, bottom, right, tileIcon );
     * Paints the matte border.
    public void paintBorder(Component c, Graphics g, int x, int y, int width, int height) {
         super.paintBorder( c, g, x, y, width, height );
        Insets insets = getBorderInsets(c);
        Color oldColor = g.getColor();
        g.translate(x, y);
        color = c.getBackground();
        if ( color == null )
             color = Color.gray;
        // Erase part of top matte edge
        g.setColor(color);
        g.fillRect( width / 2, 0, width, insets.top);
        g.translate(-x, -y);
        g.setColor(oldColor);
     // Example use on a JPanel containing a JButton.
     public static void main( String[] args ) {
          JPanel p = new JPanel();
          p.setBorder( new PartiallyPaintedBorder( MARGIN, MARGIN, MARGIN, MARGIN, UIManager.getIcon( "FileView.computerIcon" ) ) );
          p.add( new javax.swing.JButton( "Press me" ) );
          JFrame f = new JFrame( "Tester" );
          f.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
          f.getContentPane().add( p );
          f.pack();
          f.setVisible( true );
}