Final answer:
The Open-Closed Principle in object-oriented software construction dictates that software should be open for extension but closed for modification. It can be implemented using interfaces and abstract classes, which allow new functionality to be added without altering existing code.
Step-by-step explanation:
Understanding the Open-Closed Principle
The Open-Closed Principle (OCP) is a fundamental concept in object-oriented software construction (OOSC). It asserts that software entities such as modules, classes, functions, etc. should be open for extension, meaning that their behavior can be extended or changed as the user requirements change. Concurrently, they should be closed for modification, indicating that the existing source code should not be modified to accommodate new functionality. This dichotomy presents a challenge often referred to as a dilemma.
Solving the Open-Closed Principle Dilemma in OOSC
In object-oriented programming (OOP), the OCP can be resolved through the use of interfaces and abstract classes. An interface provides a contract that implementing classes must follow, while abstract classes can contain default behavior and abstract methods to be overridden. By using these constructs, new functionality can be introduced by creating new classes that implement the interfaces or inherit from the abstract classes without altering the existing code. For example, suppose a software application uses an PaymentProcessor interface. As payment methods evolve, new classes implementing them PaymentProcessor can be added without modifying the underlying system code. This keeps the existing code base stable and minimizes the risk of breaking existing functionality when adding new features.