Abstract classes and interfaces: default, static and private interface methods

An abstract class is declared with abstract and cannot be instantiated with new. It may contain abstract methods, which have no body and end with a semicolon, alongside ordinary methods, fields and constructors. A concrete (non-abstract) subclass must implement every inherited abstract method; an abstract subclass may leave them for its own subclasses. An abstract method cannot be private, static or final, because each of those would stop it from being overridden. A class with an abstract method must itself be abstract.