AP Comp Sci: thoughts on JPanel

Asked a fairly open-ended question on a recent exam: "What's the difference between the ColorPanel classes we've been creating & using these past few weeks, and the JPanel class?"

During grading, following came to me: one way of thinking about JPanel is that, for our purposes, it exists primarily to be extended. It is like unmolded clay -- a framework -- that we want to build on. But we wouldn't really use it very much just on its own -- it is too boring.