Java面试题：通过实例说明工厂模式和抽象工厂模式的用法，以及它们在解耦中的作用

工厂模式和抽象工厂模式是创建型设计模式中的两种，主要用于对象的创建，并且通过将对象的创建过程封装起来，来实现代码的解耦和灵活性。下面通过具体实例来说明这两种模式的用法及其在解耦中的作用。

工厂模式（Factory Method Pattern）

工厂模式通过定义一个创建对象的接口，让子类决定实例化哪一个类。工厂方法使一个类的实例化延迟到其子类。

实例说明

假设我们有一个交通工具接口 Vehicle 以及具体实现类 Car 和 Bike。我们通过工厂模式来创建这些交通工具对象。

接口和实现类

// Vehicle.java
public interface Vehicle {void drive();
}// Car.java
public class Car implements Vehicle {@Overridepublic void drive() {System.out.println("Driving a car.");}
}// Bike.java
public class Bike implements Vehicle {@Overridepublic void drive() {System.out.println("Riding a bike.");}

工厂类

// VehicleFactory.java
public abstract class VehicleFactory {public abstract Vehicle createVehicle();
}// CarFactory.java
public class CarFactory extends VehicleFactory {@Overridepublic Vehicle createVehicle() {return new Car();}
}// BikeFactory.java
public class BikeFactory extends VehicleFactory {@Overridepublic Vehicle createVehicle() {return new Bike();}

使用工厂模式

public class Main {public static void main(String[] args) {VehicleFactory carFactory = new CarFactory();Vehicle car = carFactory.createVehicle();car.drive(); // 输出: Driving a car.VehicleFactory bikeFactory = new BikeFactory();Vehicle bike = bikeFactory.createVehicle();bike.drive(); // 输出: Riding a bike.}
}

解耦作用

通过工厂模式，Main 类不需要知道具体的交通工具类，只需要知道工厂类和接口 Vehicle。这使得代码更加灵活，增加了新类型的交通工具时不需要修改现有代码。

抽象工厂模式（Abstract Factory Pattern）

抽象工厂模式提供一个创建一系列相关或相互依赖对象的接口，而无需指定它们具体的类。

实例说明

假设我们有一个家具工厂，可以创建椅子和沙发。我们通过抽象工厂模式来实现。

接口和实现类

// Chair.java
public interface Chair {void sitOn();
}// Sofa.java
public interface Sofa {void lieOn();
}// VictorianChair.java
public class VictorianChair implements Chair {@Overridepublic void sitOn() {System.out.println("Sitting on a Victorian chair.");}
}// ModernChair.java
public class ModernChair implements Chair {@Overridepublic void sitOn() {System.out.println("Sitting on a modern chair.");}
}// VictorianSofa.java
public class VictorianSofa implements Sofa {@Overridepublic void lieOn() {System.out.println("Lying on a Victorian sofa.");}
}// ModernSofa.java
public class ModernSofa implements Sofa {@Overridepublic void lieOn() {System.out.println("Lying on a modern sofa.");}

抽象工厂类和具体工厂类

// FurnitureFactory.java
public interface FurnitureFactory {Chair createChair();Sofa createSofa();
}// VictorianFurnitureFactory.java
public class VictorianFurnitureFactory implements FurnitureFactory {@Overridepublic Chair createChair() {return new VictorianChair();}@Overridepublic Sofa createSofa() {return new VictorianSofa();}
}// ModernFurnitureFactory.java
public class ModernFurnitureFactory implements FurnitureFactory {@Overridepublic Chair createChair() {return new ModernChair();}@Overridepublic Sofa createSofa() {return new ModernSofa();}
}

使用抽象工厂模式

public class Main {public static void main(String[] args) {FurnitureFactory victorianFactory = new VictorianFurnitureFactory();Chair victorianChair = victorianFactory.createChair();Sofa victorianSofa = victorianFactory.createSofa();victorianChair.sitOn(); // 输出: Sitting on a Victorian chair.victorianSofa.lieOn();  // 输出: Lying on a Victorian sofa.FurnitureFactory modernFactory = new ModernFurnitureFactory();Chair modernChair = modernFactory.createChair();Sofa modernSofa = modernFactory.createSofa();modernChair.sitOn(); // 输出: Sitting on a modern chair.modernSofa.lieOn();  // 输出: Lying on a modern sofa.}
}