Learn common design patterns: Improve your Java development skills

Improving Java development skills: Mastering common design patterns requires specific code examples

Design patterns are important concepts in software development. They provide a common set of Solutions to common problems in software design and development. Mastering common design patterns is very important for Java developers. They can help developers write more maintainable, reusable and extensible code.

This article will introduce some common design patterns and help readers better understand and apply these patterns through specific code examples.

1. Singleton Pattern
   The singleton pattern is a creational pattern that is used to ensure that a class has only one instance and provides a global access point. In Java development, we often use the singleton pattern to manage global resources, such as database connections, log objects, etc. The following is a simple singleton pattern code example:

public class Singleton {
    private static Singleton instance;

    private Singleton() {}

    public static Singleton getInstance() {
        if (instance == null) {
            instance = new Singleton();
        }
        return instance;
    }
}

2. Factory Pattern (Factory Pattern)
   Factory pattern is a creation pattern that is used to encapsulate the creation process of objects. Through the factory pattern, we can hide the instantiation details of the object and provide a unified interface to create objects through the factory class. The following is a simple factory pattern code example:

public interface Shape {
    void draw();
}

public class Circle implements Shape {
    @Override
    public void draw() {
        System.out.println("Drawing a circle.");
    }
}

public class Rectangle implements Shape {
    @Override
    public void draw() {
        System.out.println("Drawing a rectangle.");
    }
}

public class ShapeFactory {
    public Shape createShape(String type) {
        if (type.equalsIgnoreCase("circle")) {
            return new Circle();
        } else if (type.equalsIgnoreCase("rectangle")) {
            return new Rectangle();
        }
        return null;
    }
}

3. Observer Pattern (Observer Pattern)
   Observer pattern is a behavioral pattern used to implement communication between objects. One-to-many dependency. When an object changes, all its dependent objects are automatically notified and updated. The following is a simple observer pattern code example:

public interface Observer {
    void update();
}

public class Subject {
    private List<Observer> observers = new ArrayList<>();

    public void attach(Observer observer) {
        observers.add(observer);
    }

    public void detach(Observer observer) {
        observers.remove(observer);
    }

    public void notifyObservers() {
        for (Observer observer : observers) {
            observer.update();
        }
    }
}

public class ConcreteObserver implements Observer {
    @Override
    public void update() {
        System.out.println("Received update from subject.");
    }
}

In addition to the above examples, there are many other commonly used design patterns, such as adapter pattern, decorator pattern, strategy pattern, etc. By learning and mastering these patterns, Java developers can improve code reusability, maintainability, and scalability.

In summary, mastering common design patterns is very important for Java developers. Through specific code examples, this article introduces some common design patterns, including singleton pattern, factory pattern and observer pattern. I hope readers can learn and apply these patterns in depth to improve their Java development skills.

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