JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech IV DESIGN PATTERNS Previous Question Paper (September - 2021 - R15)

Design patterns are categorized by their purpose (Creational, Structural, Behavioral) and scope (Class, Object). The relationships among them are defined by how they interact to solve recurring software design problems. Creational patterns handle object creation, Structural patterns deal with object composition, and Behavioral patterns focus on communication between objects. For example, a Factory Method (Creational) might be used to create objects that are then organized by a Composite (Structural) pattern and controlled by an Observer (Behavioral) pattern.

To select a design pattern, follow these systematic steps:

• Analyze the problem: Identify the specific design challenge, such as object creation complexity, class hierarchy issues, or communication decoupling.
• Review the Intent: Consult the 'Intent' section of various patterns to see which ones address your specific problem.
• Examine Consequences: Evaluate the trade-offs, such as memory usage, flexibility, and complexity, associated with each candidate pattern.
• Consider Relationships: Look for patterns that are often used together or are alternatives to one another.
• Prototype: Implement a small-scale version to verify if the pattern effectively solves the problem without introducing unnecessary overhead.

To use a design pattern effectively, follow this implementation process:

• Understand the structure: Study the participants (classes and objects) and their collaborations as defined in the pattern's class diagram.
• Identify participants: Map the abstract roles in the pattern to the concrete classes in your application.
• Define interfaces: Establish the necessary interfaces or abstract classes to ensure loose coupling between components.
• Implement the logic: Write the code for the specific pattern, ensuring that the interaction between classes adheres to the pattern's design principles.
• Refactor: Integrate the pattern into the existing code base, refactoring where necessary to ensure the design remains clean and maintainable.