Use Java's extends keyword to derive a child class from a parent class, invoke parent class constructors and methods, override methods, and more.

Although Java prevents a developer from extending more than one class, a simple trick can be used to simulate multiple inheritance. I have used this technique in both a Swing application and a Web ...

If you want to extend the Expr class, you must explicitly add the permits clause. Only a library developer can add that clause. Sealed class rules Sealed classes offer precise control over inheritance ...