How do you create different shaped borders?

Question

I need to create lots of different shaped borders that can be selected for a particular component, I know that you have to either extend AbstractBorder or implement Border interface, but I don't really know how to get the shape that I want, the most basic of which is a circle.
Also will the component 'know' how to size the border so that the child components fit within it with no overlap?
if anyone has an example border class they could donate to ease my confusion, i would be most grateful

Answer 1

I have attached code for a border that draws a circle. If the insets are not large enough, then the child component will overlap. The large the child component needs to be, the large the insets should be in order for the oval to not be broken.
// Border class
public class OvalBorder implements javax.swing.border.Border {
    // insets used by the parent component for sizing the child component
    java.awt.Insets insets;
    public OvalBorder( ) {
        this( new java.awt.Insets( 20, 20, 20, 20 ) );
    public OvalBorder( java.awt.Insets insets ) {
        this.insets = insets;
    // Tell the parent component not to pain a backgroun underneath the border.
    public boolean isBorderOpaque( ) {
        return false;
    // Paint a simple oval border.
    public void paintBorder( java.awt.Component component, java.awt.Graphics g, int x, int y, int width, int height ) {
        g.setColor( java.awt.Color.white );
        g.fillOval( x, y, width, height );
        g.setColor( java.awt.Color.black );
        g.drawOval( x, y, width, height );
    // Return the insets that the parent component will use to size
    // the child component
    public java.awt.Insets getBorderInsets( java.awt.Component p1 ) {
        // Must do a clone so an outside source does not mess up the inset object.
        return (java.awt.Insets)insets.clone( );
    // A simple frame example of the border
    public static void main( String[ ] args ) {
        javax.swing.JFrame frame = new javax.swing.JFrame( );
        frame.setDefaultCloseOperation( javax.swing.JFrame.EXIT_ON_CLOSE );
        javax.swing.JPanel panel = new javax.swing.JPanel( new java.awt.GridLayout( 2, 1, 0, 0 ) );
        panel.setBorder( new OvalBorder( ) );
        frame.setContentPane( panel );
        javax.swing.JButton add = new javax.swing.JButton( "Add" );
        javax.swing.JButton minus = new javax.swing.JButton( "Minus" );
        frame.getContentPane( ).add( add );
        frame.getContentPane( ).add( minus );
        Inc inc = new Inc( add, minus, frame );
        add.addActionListener( inc );
        minus.addActionListener( inc );
        frame.pack( );
        frame.setVisible( true );
// A support class that will cause the frame to resize equaly in both directions.
class Inc implements java.awt.event.ActionListener {
    javax.swing.JButton add;
    javax.swing.JButton minus;
    javax.swing.JFrame frame;
    java.awt.Dimension pref;
    public Inc( javax.swing.JButton add, javax.swing.JButton minus, javax.swing.JFrame frame ) {
        this.add = add;
        this.minus = minus;
        this.frame = frame;
        pref = minus.getPreferredSize( );
        pref.width = pref.height<<1;
    public void actionPerformed( java.awt.event.ActionEvent event ) {
        if ( event.getSource( ) == add ) {
            pref.width+=2;
            pref.height++;
        } else {
            pref.width-=2;
            pref.height--;
        add.setPreferredSize( pref );
        minus.setPreferredSize( pref );
        System.out.println( pref );
        frame.pack( );
}