Classes and objects in Java must be initialized before they are used. You’ve previously learned that class fields are initialized to default values when classes are loaded, and that objects are ...

Packages can store classes and interfaces, as well as subpackages, which are packages nested within other packages. A package has a name, which must be a non-reserved identifier; for example, java.

Sealed classes in Java let developers limit the creation and use of subclasses and preserve the class hierarchy. Here is how sealed classes in Java work.