设计模式总结之工厂模式

除了直接使用new之外，还有更多制造对象的方法。工厂模式可以使实例化的活动不公开进行，也可以解决因初始化而造成的耦合问题。工厂模式是一种常见的模式，在安卓中BitmapFactory也是使用的简单工厂。

简单工厂：

public class Test {
	public static void main(String[] args) throws Exception{
		Auto auto = (Auto) CarFactory.createCraByType("Auto");
		Chev chev = (Chev) CarFactory.createCraByType("Chev");
		Car car = CarFactory.createCraByType("aa");
		
	}
}

public class CarFactory {
	public static Car createCraByType(String carType) throws Exception{
		if (carType.equals("Auto")) {
			return new Auto();
		}else if (carType.equals("Chev")) {
			return new Chev();
		}else {
			throw new Exception(){
				@Override
				public String getMessage() {
					return "not find the car you want";
				}
			};
		}
	}

}

public interface Car {
}
public class Auto implements Car{

	public Auto() {
		System.out.println("auto is created");
	}
}
public class Chev implements Car{
	public Chev() {
		System.out.println("chev is created");
	}
}

介绍完简单工厂，接下来具体介绍一下工厂方法和抽象工厂。

工厂方法：定义了一个创建对象的接口，但由子类决定要实例化的类是哪一个。工厂方法让类把实例化推迟到子类。其实要我理解工厂方法强调的是工厂和方法，不同的工厂有相同的方法，但是产生的却是不同工厂的产品。

public interface Car {
}

public class Auto implements Car{

	public Auto() { 
		System.out.println("auto is created");
	}

}

public class Chev implements Car{
	public Chev() {
		System.out.println("Chec is created");
	}
	
}

public interface CarFactory {
	public Car createCar();

}

public class AutoCarFactory implements CarFactory{

	@Override
	public Car createCar() {
		return new Auto();
	}
	
}

public class ChevFactory implements CarFactory {

	@Override
	public Car createCar() {
		return new Chev();
	}

}

public class Test {
	public static void main(String[] args){
		CarFactory carFactory = new AutoCarFactory();
		carFactory.createCar();
		carFactory = new ChevFactory();
		carFactory.createCar();
	}
}

抽象工厂：提供一个接口，用于创建相关或依赖对象的家族，而不需要明确指定具体类。

public class Auto implements Car{

	public Auto() { 
		System.out.println("auto is created");
	}

}

public class AutoCarFactory implements CarFactory{

	@Override
	public Car createCar() {
		return new Auto();
	}

	@Override
	public Suv createSUV() {
		// TODO Auto-generated method stub
		return new AutoSuv();
	}
	
}

public class AutoSuv extends Suv{
	public AutoSuv() {
		System.out.println("AutoSur is created");
	}
	
}

public interface Car {
}

public interface CarFactory {
	public Car createCar();
	public Suv createSUV();
}

public class Chev implements Car{
	public Chev() {
		System.out.println("Chec is created");
	}
	
}

public class ChevFactory implements CarFactory {

	@Override
	public Car createCar() {
		return new Chev();
	}

	@Override
	public Suv createSUV() {
		// TODO Auto-generated method stub
		return new ChevSuv();
	}
}

public class ChevSuv extends Suv{
		public ChevSuv() {
			System.out.println("ChevSuv is created");
		}
}

public interface Suv {

}

public class Test {
	public static void main(String[] args){
		CarFactory carFactory = new AutoCarFactory();
		Car car = carFactory.createCar();
		Suv suv =carFactory.createSUV();
		carFactory = new ChevFactory();
		car = carFactory.createCar();
		suv = carFactory.createSUV();
	}
}

其实个人认为 工厂方法和 抽象工厂的根本区别在于是要产生单个产品还是产品家族。