《大话设计模式》--建造者模式

题目：建造两个产品，这两个产品都有两个部件

abstract class Builder {
    public abstract void buildPartA();

    public abstract void buildPartB();

    public abstract Product getResult();
}

public class ConcreteBuilder1 extends Builder {
    private Product product = new Product();

    @Override
    public void buildPartA() {
        product.add("部件A");
    }

    @Override
    public void buildPartB() {
        product.add("部件B");
    }

    @Override
    public Product getResult() {
        return product;
    }
}

public class ConcreteBuilder2 extends Builder {
    private Product product = new Product();

    @Override
    public void buildPartA() {
        product.add("部件X");
    }

    @Override
    public void buildPartB() {
        product.add("部件Y");
    }

    @Override
    public Product getResult() {
        return product;
    }
}

public class Director {
    public void construct(Builder builder) {
        builder.buildPartA();
        builder.buildPartB();
    }
}

public class Product {
    List<String> parts = new ArrayList<>();

    public void add(String part) {
        parts.add(part);
    }

    public void show() {
        System.out.println("产品创建。。。");
        for (String part : parts) {
            System.out.println(part);
        }
    }

}

public class Action {
    public static void main(String args[]) {
        Director director = new Director();
        Builder b1 = new ConcreteBuilder1();
        Builder b2 = new ConcreteBuilder2();

        director.construct(b1);
        Product p1 = b1.getResult();
        p1.show();

        director.construct(b2);
        Product p2 = b2.getResult();
        p2.show();
    }
}

打印结果：

产品创建。。。
部件A
部件B
产品创建。。。
部件X
部件Y

其实，Action类中

director.construct(b1);

实际调用的就是

b1.buildPartA();

b1.buildPartB();

Director是建造的指挥者，通过父类调用子类实际的操作。