The release of Java SE 15 in Sept 2020 will introduce "sealed classes" (JEP 360) as a preview feature. A sealed class is a class or interface which restricts which other classes or interfaces may ...

public final class StockTransaction extends Transaction { } How sealed classes work. The key concept with sealed classes is that they are declared using the sealed keyword, followed by the permits ...

The Float and Double classes extend Ellipse2D, ... For example, the Matcher class, in java.util.regex, provides a results() method that returns a stream of match results.

Abstract classes and interfaces in Java serve fundamentally different purposes. Learn the differences between these Java language elements and how to use them in your programs.