Why the part will not have add() and remove() ways whereas Jcomponent Have add() And Remove() ways?

Sorry, but that question cannot be understood in english.
Can you try to explain it better please?

JComponent is the base class for all Swing components except the top-level containers(JFrame, JDialog, JApplet).
It does not define any add methods, but it does inherit a number of overloaded add methods from its underlying awt classes, viz
add(PopupMenu) and a number of variants on add(Component).
Those methods are inherited by all Swing components, even if they make no sense (eg add a component to a JLabel).
So I don't understand the question "Why the part will not have add() and remove() ways?"