What is common package?

Packages with names like base or common are often found when functionality common to two or more related facilities , for example common types between a client and server or a server and its mock, has been refactored into a separate package.

Read more

What is built in Java class?

In Java, all classes (built-in or user-defined) are (implicitly) subclasses of Object . Using an array of Object in the List class allows any kind of Object (an instance of any class) to be stored in the list. However, primitive types (int, char, etc) cannot be stored in the list.

Read more