g.setColor (Color.red);
Graphics clippedGraphics = g.create();
clippedGraphics.drawRect (0,0,100,100);
clippedGraphics.clipRect (25, 25, 50, 50);
clippedGraphics.drawLine (0,0,100,100);
clippedGraphics.dispose();
clippedGraphics=null;
g.drawLine (0,100,100,0);