Software Design

The Adapter Design Pattern is a structural pattern that allows objects with incompatible interfaces to work together. It acts as a bridge, converting the interface of a class into another interface that clients expect. This pattern is useful when you want to use an existing class but its interface doesn’t match the one you need. Components of the Adapter Design Pattern: Target: The interface that the client expects to use. Adapter: Converts the interface of the Adaptee into the Target interface....

The Visitor Design Pattern is a behavioral pattern that allows you to define new operations on objects without changing their classes. It involves separating algorithms from the objects on which they operate. This pattern is useful when you need to perform operations on a group of objects with different types without altering their classes. Components of the Visitor Design Pattern: Visitor Interface: Declares a visit method for each type of element that can be visited....

The Template Design Pattern is a behavioral pattern that defines the skeleton of an algorithm in a base class but allows subclasses to override specific steps of the algorithm without changing its structure. This pattern is useful when you have a common sequence of steps that are shared among multiple subclasses but may vary in certain details. Components of the Template Design Pattern: Abstract Class (Template): Defines the template method that outlines the algorithm’s structure and includes some default behavior....

The Observer Pattern is a behavioral design pattern used to define a one-to-many dependency between objects. When one object (the subject) changes its state, all dependent objects (observers) are notified and updated automatically. This pattern is commonly used in scenarios where changes in one part of an application need to be reflected in other parts without tightly coupling the components. Components of the Observer Pattern: Subject: The object that maintains a list of observers and notifies them of any changes....

The Command Design Pattern is a behavioural design pattern that turns a request into a stand-alone object containing all the information about the request. This pattern allows you to parameterize objects with operations, delay the execution of an operation, or queue a request for execution. Simple Example: Imagine you have a remote control that can turn on and off a light. The Command Pattern can be used to encapsulate these operations into objects....

Imagine you’re sending a package. It goes through various checkpoints: sorting, security, customs, etc. Each checkpoint decides whether to handle the package or pass it on to the next. This is similar to the Chain of Responsibility pattern. Key Idea: A request is passed along a chain of objects. Each object decides whether to handle or pass the request to the next. This creates a loose coupling between the sender and receiver....

The Interpreter Pattern is a design pattern used to define a grammatical representation of a language and provide an interpreter to deal with this grammar. It is useful for interpreting expressions in a language. Simple Explanation: Grammar: Define the rules of the language. Expressions: Create classes for each rule in the grammar. Context: Store information that might be needed during interpretation. Interpreter: Evaluate the expressions based on the rules. Example: Imagine a simple language for arithmetic expressions with numbers, addition, and multiplication....

The Iterator pattern provides a way to access the elements of a collection without exposing its internal structure. It promotes loose coupling between the collection and the code that uses it. Key Components: Iterator: Defines the interface for accessing and traversing elements in a collection. Concrete Iterator: Implements the Iterator interface and keeps track of the current position in the traversal. Aggregate: Defines an interface for creating an Iterator object. Concrete Aggregate: Implements the Aggregate interface and creates a Concrete Iterator....

Understanding the Problem Imagine you’re building a text editor. Users often make mistakes or want to revert changes. How can you allow them to undo their actions without exposing the internal state of the document? The Memento Solution The Memento pattern provides a solution by capturing and storing the internal state of an object without violating encapsulation. Key Players: Originator: The object whose state needs to be saved (e.g., the text editor)....

The Mediator pattern promotes loose coupling between objects by introducing a mediator that handles communication between them. This reduces dependencies and makes the system more flexible and maintainable. A Simple Chat Room Example Let’s consider a basic chat room application with multiple users. Instead of users communicating directly with each other, they’ll send messages to a chat room (the mediator), which then broadcasts the message to all users. 1. Define the Mediator Interface: interface ChatRoom { void registerUser(User user); void send(String msg, User user); } 2....