Anyone have experience reusing "cell renderers" among multiple instances...

Question

I've implemented a 'light' cell renderer that sets all its attributes during the fetch to
getCellRendererComponent()
[in other words, all of the cell renderer instance vars are set during this call, wiping out the last objects settings]
In the hopes of saving memory, I wanted to create one cell renderer instance and share it among 100's of the same type of object. Realizing that all paints should perform on the single threaded GUI-EVENT-THREAD, this operation should be safe.
Anyone try this before?? Is it possible to reuse a single renderer instance among multiple Swing components? I look at the way Swing generates the default renderers if you don't specify one and it always returns a new instance ( the == is false ), yet each instance returned looks almost identical and contains references to the same objects with the same memory addresses.

Answer 1

I'm pretty much sure that sharing one instance is the default behavior. Check out installDefault() of class javax.swing.plaf.basic.BasicListUI. Here, all JList instances are initialized with a single ListCellRenderer instance.
Here's an example:public static void main(String[] arguments) {
        JFrame f = new JFrame();
        Vector v = new Vector();
        for (int i = 0; i < 10; i++)
            v.add(new Integer(i));
        JList l = new JList(v);
        l.setCellRenderer(new DefaultListCellRenderer() {
            private int val;
            public Component getListCellRendererComponent(
                JList list,
                Object value,
                int index,
                boolean isSelected,
                boolean cellHasFocus) {
                if (isSelected) {
                    setBackground(list.getSelectionBackground());
                    setForeground(list.getSelectionForeground());
                } else {
                    setBackground(list.getBackground());
                    setForeground(list.getForeground());
                setEnabled(list.isEnabled());
                setBorder(
                    (cellHasFocus)
                        ? UIManager.getBorder("List.focusCellHighlightBorder")
                        : noFocusBorder);
                val = ((Integer) value).intValue();
                setPreferredSize(new Dimension(val * 12, 12));
                return this;
            protected void paintComponent(Graphics g) {
                g.setColor(getBackground());
                g.fillRect(0, 0, getWidth(), getHeight());
                g.setColor(getForeground());
                for (int i = 0; i < val; i++)
                    g.fillOval(i * 12, 1, 10, 10);
        f.getContentPane().add(new JScrollPane(l));
        f.pack();
        f.show();
    }Hope that helps,
bye