Every Java class inherits from Object, so familiarity with this superclass is fundamental to understanding the Java class hierarchy. Also see my Java tip introducing composition vs. inheritance .

Sealed classes, proposed in JEP 409 and available since Java 17, let developers limit and control how deeply a component's type hierarchy can extend. With sealed classes, a developer can essentially ...

While it seems so basic that it wouldn't require a mention, there's a basic and often violated software design principle pertaining to Java method modifiers that is in need of explanation. A public ...