Java Abstract Classes and Abstract Methods: Why Define Abstract Classes? A Basic Syntax Analysis

This article introduces Java abstract classes and abstract methods. An abstract class is a template that defines common characteristics (e.g., the "sound" of an animal), containing abstract methods (which only declare behavior without specific implementation). Its roles include unifying behavioral specifications, preventing incomplete objects, and enabling code reuse. Syntactically, an abstract class is modified with the `abstract` keyword and cannot be directly instantiated. Subclasses must implement all abstract methods (otherwise, the subclass itself remains abstract). Abstract methods cannot be `private` or `static`, but abstract classes can contain ordinary attributes and methods. When a subclass inherits an abstract class, a non-abstract subclass must fully implement the abstract methods. Abstract classes support single inheritance and are suitable for forcing subclasses to implement specific methods.