Chapter 13 - Abstract Classes and Interfaces

Abstract Classes

• Abstract classes are superclasses designed to have common features shared by subclasses.
• Declared using the abstract modifier, these classes cannot be instantiated (no object creation using new).
• Contain both data fields and methods similar to regular classes.

Abstract Methods

• An abstract method has a signature but lacks an implementation.
• Denoted with the abstract modifier and must exist within an abstract class.
• Subclasses that extend an abstract class must implement all abstract methods, whether they are used or not.

Deep Copy

• Cloning an object through a deep copy means recursively cloning all its fields.
• Ensures that the new object is entirely independent of the original object.

Interfaces

• An interface functions like a special class; each one compiles into a separate bytecode file.
• Instances of an interface cannot be created.
• Similar to abstract classes, interfaces can have data (which must be constants) and method declarations without implementations.
• Java enforces single inheritance, where a class can inherit from only one superclass, but interfaces allow for multiple inheritance by implementing multiple interfaces.

Marker Interface

• A marker interface is an empty interface serving to indicate that all implementing classes share certain properties or behaviors.

Multiple Inheritance

• This refers to a class extending multiple superclasses, allowing for more complex behavior and functionality.

Shallow Copy

• In a shallow copy, all fields of the object are copied, but nested objects are not recursively cloned.

Single Inheritance

• A class can extend only one superclass, maintaining a straightforward hierarchy.

Subinterface

• A subinterface is an interface that is inherited from another interface, allowing for further specialization.