建造者模式：把对象的设置过程抽取出来。

对于那些设置过程比较复杂的对象，可以把这一个过程抽取出来形成一个接口（规范）和一个设置过程，让具体的实现类和设置类去设置这个复杂的对象。

class Product{
    List<String> parts = new List<String>();
    
    public void Add(String part){
        parts.add(part);
    } 
    
    public void show(){
        foreach(String p : parts){
            System.out.println(p);
        }
    }
}

interface Builder{
    public abstract void BuildPartA();
    public abstract void BuildPartB();
    public abstract Product GetResult();
}

class ConcreteBuilder1 implements Builder{
    
    private Product product = new product();
    
    public void BuilderPartA(){
        product.add("部件A");
    }

    public void BuilderPartB(){
        product.add("部件B");
    }
    
    public Product GetResult(){
        return product;
    }
}

class ConcreteBuilder2 implements Builder{
    
    private Product product = new product();
    
    public void BuilderPartA(){
        product.add("部件X");
    }

    public void BuilderPartB(){
        product.add("部件Y");
    }
    
    public Product GetResult(){
        return product;
    }
}

class Director{
    public void Construct(Builder builder){
        builder.BuildPartA();
        builder.BuildPartB();
    }
}

public class test{
    public static void main(String[] args){

        Director director = new Director();

        Builder b1 = new ConcreteBuilder1();
        Builder b2 = new COncreteBuilder2();

        direct.Construct(b1);
        Product p1 = b1.GetResult();
        p1.show();


        direct.Construct(b2);
        Product p2 = b2.GetResult();
        p2.show();
    }
}