Can a container contain a container?
Yes. You see this when the main window of a browser contains frames, which themselves contain other components.
The component classes that make up the AWT and Swing are related to each other by inheritance. When you learn new GUI components it is important to see how they relate to other components.
In Java,
there is a pre-defined class that is the ultimate ancestor of all other classes.
This class is called Object
.
Object
defines the basic nature of all Java objects.
Much of what goes on behind the scenes when a Java program is running
is defined by Object
.
So, for example a small part of the Java class hierarchy looks like this:
The "clouds" convey the idea that these are class
definitions, not objects.
The diagram shows that the classes Boolean
, Character
,
Component
, String
, and many others
have Object
as a direct ancestor.
The cloud for the Component
class is dotted
to show that it is an abstract class.