Classes, fields, methods, constructors, and objects are the building blocks of object-based Java applications. This Java tutorial teaches you how to declare classes, describe attributes via fields ...

For example, suppose package physics contains a Math class that’s identical to java.lang ‘s Math class in that it implements the same PI constant and trigonometric methods.

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.