If you can't see them until you resize the window, then there are any number of possible issues. The objects might be too big to be drawn within the window, so they don't show up until you make the window big enough, you may have bits of code interfering with each other, you have not yet discovered pack()..
It is also hard o say what classes you should extend, because we don't know what it is you are doing. When I do GUI, I often extend JFrame or JPanel, depending on what it is I am doing. But it is also a good way to introduce more problems.
