The "contentPane" is the primary container for application specific components. Applications should add children to the contentPane, set its layout manager, and so on.
The contentPane may not be null.
Generally implemented with
getRootPane().setContentPane(contentPane);
contentPane | the Container to use for the contents of this JRootPane |
java.awt.IllegalComponentStateException | (a runtime exception) if the content pane parameter is null |
JRootPane.getContentPane, getContentPane
Diagram: JFrame