What is the Command and Query Responsibility Segregation (CQRS) Pattern?
- A pattern in which read and write operations are separated into separate models.
- A pattern that helps to avoid race conditions and deadlocks in multithreaded applications.
- A pattern used to implement inter-process communication.
- A pattern used to improve database performance by caching results in memory.
CQRS is a pattern that separates the responsibilities of querying data (read) from modifying data (write) into separate models, improving scalability and maintainability of the application.
What is Null Object pattern?
- A design pattern in which a special object, called the null object, is used to represent the absence of a value, avoiding the need for explicit checks for null values
- A design pattern in which an object, called the context, holds a reference to an instance of one of several possible concrete state objects, each of which represents a distinct state of the context and implements a common state interface
- A design pattern in which an object, called the decorator, adds or overrides behavior of an existing object, dynamically
- A design pattern in which an object, called the prototype, is used as a template to create new objects, without specifying their concrete classes
The Null Object pattern is a design pattern in which a special object, called the null object, is used to represent the absence of a value, avoiding the need for explicit checks for null values. The Null Object pattern is used to provide a default implementation of an interface, reducing the amount of error-prone null checks in the code. The Null Object pattern can also be used to simplify the code and reduce coupling by eliminating the need for explicit checks for null values.
What is the difference between the Decorator and Flyweight patterns?
- The Decorator pattern is used to dynamically add or override behavior of an object, while the Flyweight pattern is used to reduce the number of objects created by sharing objects that are costly to create.
- The Decorator pattern is used to dynamically add or override behavior of an object, while the Flyweight pattern is used to share objects that are costly to create.
- The Decorator pattern is used to reduce the number of objects created by sharing objects that are costly to create, while the Flyweight pattern is used to dynamically add or override behavior of an object.
- The Decorator pattern is used to share objects that are costly to create, while the Flyweight pattern is used to dynamically add or override behavior of an object.
The Decorator pattern is used to dynamically add or override behavior of an object, while the Flyweight pattern is used to share objects that are costly to create.
What is the purpose of the Decorator design pattern?
- To attach additional responsibilities to an object dynamically.
- To create objects that are interchangeable with their base classes.
- To ensure that a class has only one instance and provide a global point of access to that instance.
- To manage the flow of control between objects in a complex system.
The Decorator design pattern is used to attach additional responsibilities to an object dynamically. This allows for greater flexibility and modularity in the design of a system, as well as the ability to add or remove responsibilities as needed.
What does program to interfaces, not implementations mean?
- This means that when designing software, the focus should be on defining the behavior of the components, rather than the specific implementations of those components.
- This means that when designing software, the focus should be on defining the data structures and algorithms used by the components, rather than the specific implementations of those components.
- This means that when designing software, the focus should be on defining the input and output of the components, rather than the specific implementations of those components.
- This means that when designing software, the focus should be on defining the interfaces between different components, rather than the specific implementations of those components. This makes the code more flexible and easier to maintain, as it reduces the amount of coupling between components.
This means that when designing software, the focus should be on defining the interfaces between different components, rather than the specific implementations of those components. This makes the code more flexible and easier to maintain, as it reduces the amount of coupling between components.
What is the Null Object pattern?
- A creational design pattern that provides a way to instantiate an object in a superclass, but allow subclasses to alter the type of objects that will be created.
- A design pattern used to ensure a class has only one instance, while providing a global access point to this instance for the entire system.
- A software design pattern that enables an object to be passed around as a value.
- The Null Object pattern is a behavioral design pattern that provides a default object as a representative of "null" in the context of design patterns.
The Null Object pattern is a behavioral design pattern that provides a default object as a representative of "null" in the context of design patterns.
What is Command pattern?
- A design pattern that converts a request into a standalone object, allowing the client to parametrize objects with different requests, queue a request, or log requests
- A design pattern that passes a request through a chain of objects, allowing the objects in the chain to either handle the request or pass it on to the next object in the chain
- A design pattern that provides a simplified interface to a complex system, allowing the client to interact with the system through a single, unified interface
- A design pattern that uses shared objects to support large numbers of similar objects efficiently
Command pattern is a design pattern that converts a request into a standalone object, allowing the client to parametrize objects with different requests, queue a request, or log requests. The pattern involves creating a command class that encapsulates the request as an object, and passes the request to the invoker object. The invoker object then executes the command. This pattern can be useful in situations where you want to decouple the client from the receiver of the request, and where you want to provide a unified interface for undo and redo operations.
What is the difference between the State and Strategy patterns?
- None of the above
- The State and Strategy patterns are the same
- The State pattern allows an object to alter its behavior when its internal state changes, while the Strategy pattern allows an object to change its behavior based on the context it is in
- The State pattern allows an object to change its behavior based on the context it is in, while the Strategy pattern allows an object to alter its behavior when its internal state changes
The State pattern allows an object to alter its behavior when its internal state changes, while the Strategy pattern allows an object to change its behavior based on the context it is in
What is the Visitor pattern?
- A behavioral design pattern that lets you pass requests along a dynamic chain of receivers until one of them handles it.
- A behavioral design pattern that separates an algorithm from an object structure on which it operates. The pattern allows you to define a new operation without changing the classes of the objects on which it operates.
- A creational design pattern that uses factory methods to deal with the problem of creating objects without specifying the exact class of object that will be created.
- A structural design pattern that allows you to compose objects into tree structures to represent part-whole hierarchies.
A behavioral design pattern that separates an algorithm from an object structure on which it operates. The pattern allows you to define a new operation without changing the classes of the objects on which it operates.
Name some of the design patterns used in JDK library.
- Abstract Factory, Builder, Factory Method, Singleton
- Adapter, Facade, Observer, Prototype
- Chain of Responsibility, Command, Interpreter, Iterator
- Decorator, Mediator, State, Strategy
Some of the design patterns used in the JDK library include Decorator, Mediator, State, and Strategy. These patterns are used in various classes and APIs of the Java Standard Library to provide a clean and efficient implementation of common design problems.