Why 'JButton' is-a 'Container' in javax.swing?

As per the class hierarchy in java.awt.*, class Button & class Label is-a class Component, and Component is not a Container, which make sense to me.

As per the redesign of class hierarchy in javax.swing.*, class JButton is-a class JComponent in-turn class JComponent is-a class Container,

So, What does it mean to say that, class JButton or class JRadioButton is-a class Container? How could one think of using button or radiobutton be used as container in GUI programming?

Note: I am java beginner.