What's the difference between the root pane and the top-level container, in Swing?

Question

I understand that every top level container has some layers:

root pane
layer pane
content pane
glass pane

but I don't understand whether the root pane is the top level container itself.

What is the relationship between a pane and a container? In fact, when I return a pane with getContentPane(), the object is of type Container!

Answer 1

You also have a JFrame. Read more on How to Use Root Panes.

From JRootPane:

The "heavyweight" components (those that delegate to a peer, or native component on the host system) are shown with a darker, heavier box. The four heavyweight JFC/Swing containers (JFrame, JDialog, JWindow, and JApplet) are shown in relation to the AWT classes they extend. These four components are the only heavyweight containers in the Swing library.