建造者模式

封装一个产品的构造过程，并允许按步骤构造

类图

 

 （图来自wiki）

示例

public class Product {
    private String name;
    private String descripe;

    public void setDescripe(String descripe) {
        this.descripe = descripe;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "["+name+":"+descripe+"]";
    }
}

public interface Builder {
    void buildName();
    void buildDescripe();
    Product getProduct();
}

public class ConcreteBuilderA implements Builder{
    Product product;
    public ConcreteBuilderA(){
        product = new Product();
    }

    @Override
    public void buildName() {
        product.setName("ProductA");
    }

    @Override
    public void buildDescripe() {
        product.setDescripe("this is ProductA");
    }

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

public class ConcreteBuilderB implements Builder {
    Product product;

    public ConcreteBuilderB() {
        product = new Product();
    }

    @Override
    public void buildName() {
        product.setName("ProductB");
    }

    @Override
    public void buildDescripe() {
        product.setDescripe("this is ProductB");
    }

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

public class Director {
    Builder builder;
    public Director(Builder builder){
        this.builder = builder;
    }
    void construct(){
        builder.buildDescripe();
        builder.buildName();
    }
    public Product getProduct(){
        return  builder.getProduct();
    }
}

//测试
public class Client {
    public static void main(String[] args){
        Director directorA = new Director(new ConcreteBuilderA());
        directorA.construct();
        Product productA = directorA.getProduct();
        System.out.println(productA);
        Director directorB = new Director(new ConcreteBuilderB());
        directorB.construct();
        Product productB = directorB.getProduct();
        System.out.println(productB);
    }
}

运行结果

 

 建造者模式和工厂模式

• 建造者模式允许对象通过多个步骤来创建，并且可以改变过程，工厂模式只有一个步骤。