Question

I’m learning Java, and now that I’m over the packages hump, things are going smoothly. I can draw similarities between most things I’m learning with things I already know at least the concept of. But what on earth is going on with the following bit of code? Is it some form of constructor, or anonymous object?

Something obj = new Something()
{
  private static final int num = 3;

  public void meth()
  {
    // w/e
  }
};

Answer 1

/**
 * Notice there's only one thing in this that isn't defined:
 * It still needs public abstract void triggerEvent();
 */
public abstract static class TopButton extends JPanel implements MouseListener {
        protected ButtonPanel parent;
        private String text;
        public TopButton(ButtonPanel bp, String text) { parent = bp; this.text = text; addMouseListener(this); }
        public void mouseClicked(MouseEvent e) { triggerEvent(); }
        public void mouseEntered(MouseEvent e) { }
        public void mouseExited(MouseEvent e) { }
        public void mousePressed(MouseEvent e) { }
        public void mouseReleased(MouseEvent e) { }
        public abstract void triggerEvent();
        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            Color oldColor = g.getColor();
            Font oldFont = g.getFont();
                Font newFont = new Font(oldFont.getName(),oldFont.getStyle(),oldFont.getSize());
                g.setFont(newFont);
                g.setColor(Color.black);
                g.drawString(text, 20, 20);
            g.setFont(oldFont);
            g.setColor(oldColor);
        }
    }

Now, when I actually define my buttons, I do this. By providing the one line it needs, the only thing that makes it different from others. Now I could make a new file for each one, and define a new class for each one. This is much simpler.

private static void loadButtonPanelButtons() {
    /* This button should tell the parent to bring up the save screen */
    TopButton save = new TopButton(buttonPanel,"Save") {
        public void triggerEvent() { parent.triggerSave(); }
    };
    save.setBorder(LineBorder.createBlackLineBorder());
    buttonPanel.add(save);

    /* This button should tell the parent to bring up the load screen */
    TopButton load = new TopButton(buttonPanel,"Load") {
        public void triggerEvent() { parent.triggerLoad(); }
    };
    load.setBorder(LineBorder.createBlackLineBorder());
    buttonPanel.add(load);

    TopButton addTile = new TopButton(buttonPanel,"Add Tile") {
        public void triggerEvent() { parent.triggerAddTile(); }
    };
    addTile.setBorder(LineBorder.createBlackLineBorder());
    buttonPanel.add(addTile);

    TopButton saveTiles = new TopButton(buttonPanel,"Save Tiles") {
        public void triggerEvent() { parent.triggerStyleSave(); }
    };
    saveTiles.setBorder(LineBorder.createBlackLineBorder());
    buttonPanel.add(saveTiles);
}

Now, when I handle the buttons being pressed, remember back in the definition of TopButton… there was

    public void mouseClicked(MouseEvent e) { triggerEvent(); }

We know triggerEvent() eventually gets defined. We can define it on a per-button basis, and when the panel gets clicked, no matter what we defined triggerEvent() to be, it gets called.