public void testEquals() {
        
        XYDataItem i1 = new XYDataItem(1.0, 1.1);
        XYDataItem i2 = new XYDataItem(1.0, 1.1);
        assertTrue(i1.equals(i2));
        assertTrue(i2.equals(i1));

        i1.setY(new Double(9.9));
        assertFalse(i1.equals(i2));

        i2.setY(new Double(9.9));
        assertTrue(i1.equals(i2));