What are the commonly used design patterns in java frameworks?

Necessary Java framework design patterns: Singleton pattern: ensures that a class is instantiated only once and provides a global access point. Factory Pattern: Responsible for creating objects, allowing the use of different types of objects without changing the code. Strategy pattern: Defines a family of algorithms and allows selection of specific algorithms. Decorator Pattern: Dynamically extends object functionality without modifying the original object. Proxy pattern: Provide an object to act as a proxy for another object, controlling access to the original object or enhancing its functionality.

Essential design patterns in the Java framework

The design pattern is a proven, universal, reusable code structure. They provide elegant and maintainable solutions to common programming problems. In a Java framework, a deep understanding of these patterns is crucial. Here are some of the most common patterns:

1. Singleton pattern:
Ensure that a class is instantiated only once. This pattern simplifies resource management and consistency by providing a global access point.

public class Singleton { private static Singleton instance; private Singleton() { // Private constructor to prevent external instantiation } public static Singleton getInstance() { if (instance == null) { instance = new Singleton(); } return instance; } }

2. Factory pattern:
Responsible for creating objects without specifying their specific classes. It allows applications to use different types of objects without changing the code.

public interface ShapeFactory { Shape createShape(String type); } public class CircleFactory implements ShapeFactory { @Override public Shape createShape(String type) { if (type.equals("CIRCLE")) { return new Circle(); } else { return null; } } }

3. Strategy mode:
Define a series of algorithms and allow the client to select a specific algorithm without affecting other code. It provides a loosely coupled, configurable way to handle different behaviors.

public interface PaymentStrategy { void pay(double amount); } public class CreditCardPaymentStrategy implements PaymentStrategy { @Override public void pay(double amount) { // Process credit card payment } }

4. Decorator pattern:
Dynamically add additional responsibilities to the object. It allows extending the functionality of the original object without modifying it.

public class Shape { protected String color; public String getColor() { return color; } public void setColor(String color) { this.color = color; } } public class DecoratorShape extends Shape { protected Shape decoratedShape; public DecoratorShape(Shape decoratedShape) { this.decoratedShape = decoratedShape; } @Override public String getColor() { return decoratedShape.getColor(); } }

5. Proxy pattern:
Provide an object to act as a proxy for another object. It can be used to control access to the original object or enhance its functionality.

public class Service { public void doSomething() { // Perform some service } } public class ServiceProxy implements Service { private Service service; public ServiceProxy(Service service) { this.service = service; } @Override public void doSomething() { // Perform additional logic service.doSomething(); // Perform additional logic } }

These are just a few design patterns commonly used in Java frameworks. Mastering these patterns is critical to building maintainable, scalable, and efficient applications.

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