创建型模式 --- 工厂模式

工厂模式的几种形态：
1.简单工厂模式
2.工厂方法模式
3.抽象工厂模式

1.简单工厂模式

public interface Product {
}

public class A implements Product {
    public A(){
        System.out.println("制造了A");
    }
}


public class B implements Product {
    public B(){
        System.out.println("制造了B");
    }
}

......

public class ProductFactory {
    public static Product produce(String productName) throws Exception {
        switch (productName) {
            case "a":
                return new A();
            case "b":
                return new B();
            default:
                throw new Exception("没有该产品");
        }
    }
}

就是根据参数返回不同的实例对象

2.工厂方法模式

public interface Factory {
    public Product produce();
}

public interface Product{}

public class A implements Product {
    public A(){
        System.out.println("制造了A");
    }
}


public class B implements Product {
    public B(){
        System.out.println("制造了B");
    }
}

......

public class AFactory implements Factory {
    @Override
    public Product produce() {
        return new A();
    }
}

public class BFactory implements Factory {
    @Override
    public Product produce() {
        return new B();
    }
}

......

可以自由的扩展自定义的产品和产品工厂

3.抽象工厂模式

public interface Factory {
    public ProductA produceA();
    public ProductB produceB();
}

public interface ProductA{}
public interface ProductB{}

public class A implements ProductA {
    public A(){
        System.out.println("制造了A");
    }
}


public class B implements ProductA {
    public B(){
        System.out.println("制造了B");
    }
}
......

public class C implements ProductB {
    public C(){
        System.out.println("制造了C");
    }
}


public class D implements ProductB {
    public D(){
        System.out.println("制造了D");
    }
}
......

public class AFactory implements Factory {
    @Override
    public ProductA produceA() {
        return new A();
    }

    @Override
    public ProductB produceB() {
        return new C();
    }
}

public class BFactory implements Factory {
    @Override
    public ProductA produceA() {
        return new B();
    }

    @Override
    public ProductB produceB() {
        return new D();
    }
}
......