Issue222808

from java.awt import *
from java.awt.geom import *
from javax.swing import *


class RoundButton (JButton):

    def __init__ (self, label):
        JButton.__init__(self, label)
        s = self.preferredSize
        w = h = max(s.width, s.height)
        self.preferredSize = (w, h)
        self.contentAreaFilled = 0
        self.shape = None

    def paintComponent (self, g):
        if self.model.armed:
            g.color = Color.lightGray
        else:
            g.color = self.background
        g.fillOval(0, 0, self.size.width - 1, self.size.height - 1)
        #JButton.paintComponent(self, g)
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                     At runtime, it will complain that JButton has no
paintComponent
                     attribute.

    def paintBorder (self, g):
        g.color = self.foreground
        g.drawOval(0, 0, self.size.width - 1, self.size.height - 1)

    def contains (self, x, y):
        shape = self.shape
        if not shape or not shape.bounds.equals(self.bounds):
            self.shape = Ellipse2D.Float(0, 0, self.width, self.height)
        return self.shape.contains(x, y)


def main ():
    button = RoundButton("Jackpot")
    button.background = Color.green
    frame = JFrame()
    pane = frame.contentPane
    assert(pane)
    ^^^^^^^^^^^^^
         if this line removed, there will be NullPointerException at runtime.
    pane.background = Color.yellow
    pane.add(button)
    pane.layout = FlowLayout()
    frame.size = (150, 150)
    frame.visible = 1


if __name__ == "__main__":
    main()

The paintComponent issue is not a bug. The method is protected and the proper way of calling a protected method in the superclass is:
    self.super__paintComponent(g)

I can't remember what the assert issue was all about, but it is also fixed now.