Need help creating a "mask" effect in swing

Question

So I'm making the visual part of my connect four program. I'm trying to create the effect of dropping the piece from the top of the board to the bottom. I use the timer swing to create the animation and the animation works fine. My problem is to make the piece seem like it's between the board whereas right now the piece is in front of the board.
To see what I mean...here's the board without any pieces
Please click --> https://students.washington.edu/porrkice/connect4.jpg
Here's the board with a piece in the process of "dropping" into the bottom
Please click --> https://students.washington.edu/porrkice/connect43.jpg
The way I "drew" the board is this, and the piece is this...
  public void paintComponent(Graphics the_g) {
    super.paintComponent(the_g);
    Graphics2D g2d = (Graphics2D) the_g;
    This draws the board
    g2d.setColor(Color.yellow);
    g2d.fillRect(10, 10, my_board.getBoardsWidth() * 100, my_board.getBoardsHeight() * 100);
    g2d.setColor(Color.white);
    for (int i = 0; i < my_board.getBoardsWidth(); i++) {
      for (int j = 0; j < my_board.getBoardsHeight(); j++) {
        g2d.fillOval(MARGIN + i * 100, MARGIN + j * 100, 80, 80);
This is to draw piece
g2d.setColor(Color.red);
g2d.fillOval(MARGIN + my_x * 100, my_y, 80, 80);
}So basically, I just draw a rectangle, then draw a bunch of circles on top of it, then a circle that represents the piece...
And what I want is when the piece is dropping, when it goes pass the white circles which represents holes on the board, the yellow part between the holes will be on top of the piece
Hopefully I made my problem clear enough and someone could lend me a hand.
Edited by: inspiredone on Feb 13, 2008 12:06 AM
Edited by: inspiredone on Feb 13, 2008 12:06 AM

Answer 1

Here's an example of what Darryl suggested:
import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import javax.swing.*;
public class CompositeBoardTest extends JFrame {
     private static int size = 400;
     private static int offset = 10;
     private static int ovalSize = size/4 - offset*2;
     private static int pos = offset/2;
     private static int incr = size/4;
     public static void main( String[] args ) throws Exception {
          SwingUtilities.invokeLater( new Runnable() {
               public void run() { new CompositeBoardTest(); }
     public CompositeBoardTest() {
          super( "CompositeBoardTest" );
          setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
        Board board = new Board();
        add( board );
        setSize( size, size+34 );
          setVisible( true );
     static class Board extends JPanel implements ActionListener {
          private int[][] pieces = new int[4][4];
          private Piece addingPiece = null;
          private Timer pieceDropped = null;
          public Board() {
               setPreferredSize( new Dimension( size, size ) );
               setBounds( 0, 0, size, size );
               pieceDropped = new Timer( 10, this );
               addMouseListener( new MouseAdapter() {
                    public void mousePressed( MouseEvent e ) {
                         int column = ( e.getPoint().x-pos )/incr;
                         addPiece( column );
          protected void paintComponent( Graphics g ) {
               super.paintComponent( g );
               Graphics2D g2d = (Graphics2D) g;
               Composite comp = g2d.getComposite();
               Dimension d = getSize();
               int w = d.width;
               int h = d.height;
             BufferedImage buffImg = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
             Graphics2D gbi = buffImg.createGraphics();
             // Clear area
               g2d.setColor( Color.WHITE );
               g2d.fillRect( 0, 0, w, h );
               // Draw screen
               gbi.setColor( Color.YELLOW );
               gbi.fillRect( 0, 0, w, h );
               // Draw pieces or holes
               gbi.setColor( Color.RED );
               for ( int row = 0 ; row < 4 ; row++ ) {
                    for ( int column = 0 ; column < 4 ; column++ ) {
                         if ( pieces[row][column] == 1 ) {
                              gbi.setComposite( AlphaComposite.getInstance( AlphaComposite.SRC_OVER, 1.0f ) );
                         } else {
                              gbi.setComposite( AlphaComposite.getInstance( AlphaComposite.CLEAR, 1.0f ) );
                         gbi.fillOval( incr*column+pos, incr*row+pos, ovalSize, ovalSize );
               // Draw adding piece if we have it
               if ( addingPiece != null ) {
                    gbi.setComposite( AlphaComposite.getInstance( AlphaComposite.DST_OVER, 1.0f ) );
                    gbi.fillOval( addingPiece.x, addingPiece.y, ovalSize, ovalSize );
               // Draws the buffered image.
               g2d.drawImage(buffImg, null, 0, 0);
               g2d.setComposite( comp );
          public void addPiece( int column ) {
               if ( addingPiece == null ) {
                    if ( pieces[0][column] == 0 ) {
                         addingPiece = new Piece();
                         addingPiece.row = 0;
                         addingPiece.column = column;
                         addingPiece.x = incr*column+pos;
                         addingPiece.y = 0;
                         pieceDropped.start();
                    } else {
                         getToolkit().beep();
          public void actionPerformed( ActionEvent e ) {
               if ( addingPiece != null ) {
                    addingPiece.y += 5;
                    int row = ( addingPiece.y - pos )/incr + 1;
                    if ( row > 3 || pieces[row][addingPiece.column] == 1 ) {
                         pieces[row-1][addingPiece.column] = 1;
                         addingPiece = null;
                         pieceDropped.stop();
               repaint();
     private static class Piece {
          public int row, column, x, y;
}