Design pattern practice of interfaces and abstract classes in Java

Interfaces and abstract class design patterns in Java Interface: Mark interface: Indicates that the class has specific attributes and does not declare methods. Functional interface: declares only one abstract method, available for Lambdas and Streams. Service interface: defines business logic, and implementation class provides specific implementation. Abstract class: Abstract class pattern: defines methods and attributes that cannot be instantiated, and subclasses need to implement abstract methods. Template method pattern: Define operation steps, and subclasses can override some steps.

Design Pattern Practice of Interfaces and Abstract Classes in Java

Introduction

Interfaces and abstract classes are two important abstraction mechanisms in Java. They can be utilized effectively by following specific design patterns. This article will delve into the different design patterns of interfaces and abstract classes and provide practical code examples.

Interface

##1. Marker Interface

public interface Vehicle {
}

2. Functional Interface

@FunctionalInterface
public interface Calculate {
    int calculate(int a, int b);
}

3. Service Interface

public interface UserService {
    User getUserById(int id);
    void createUser(User user);
}

Abstract class

1. Abstract class pattern

public abstract class Animal {
    public abstract void makeSound();
}

2. Template method pattern

public abstract class Template {
    public final void execute() {
        step1();
        step2();
        step3();
    }

    protected abstract void step1();
    protected abstract void step2();
    protected abstract void step3();
}

Practical Case

Specific Product Question:

Solution:

• Tag interface: Create a Vehicle tag interface to identify all vehicle types.
• Functional interface: Create a CalculateMileage functional interface to calculate the mileage of the vehicle.
• Abstract class: Create AbstractVehicle Abstract class to define common functions of the vehicle, such as make and model.
• Service interface: Create a VehicleService service interface to define the business logic of vehicle management.

Code example

// 标记接口
public interface Vehicle {}

// 功能接口
@FunctionalInterface
public interface CalculateMileage {
    double calculate(Vehicle vehicle);
}

// 抽象类
public abstract class AbstractVehicle implements Vehicle {
    protected String make;
    protected String model;

    public String getMake() {
        return make;
    }

    public String getModel() {
        return model;
    }
}

// 服务接口
public interface VehicleService {
    List<Vehicle> getAllVehicles();
    Vehicle getVehicleById(int id);
    void createVehicle(Vehicle vehicle);
    void deleteVehicle(int id);
}

Conclusion

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