Builder（生成器）---- 对象创建型模式

1、意图
   将一个复杂对象的创建和它的表示分离，使得同样的创建过程可以创建不同的表示
2、实用性
   1）当创建复杂对象的算法应该独立于该对象的组成部分以及它们的装配方式时。
   2）当构造过程必须允许被构造的对象有不同的表示时。
3、结构


4、参与者
Builder
---为创建一个Product对象的各个部件指定抽象接口
ConcreteBuilder
---实现Builder的接口以构造和装配该产品的各个部件。
---定义并明确它所创建的表示
---提供一个检索产品的接口
Director
---构造一个使用Builder接口的对象。
Product
---表示被构造的复杂对象。ConcreteBuilder创建该产品的内部表示并定义它的装配过程。
---包含定义组成部件的类，包括将这些部件装配成最终产品的接口。
5、代码实现
   

/** "Product" */
 class Pizza {
    private String dough = "";
    private String sauce = "";
    private String topping = "";
 
 
    public void setDough(String dough)     { this.dough = dough; }
    public void setSauce(String sauce)     { this.sauce = sauce; }
    public void setTopping(String topping) { this.topping = topping; }
 }
 
 
 /** "Abstract Builder" */
 abstract class PizzaBuilder {
    protected Pizza pizza;
 
    public Pizza getPizza() { return pizza; }
    public void createNewPizzaProduct() { pizza = new Pizza(); }
 
    public abstract void buildDough();
    public abstract void buildSauce();
    public abstract void buildTopping();
 }
 
 /** "ConcreteBuilder" */
 class HawaiianPizzaBuilder extends PizzaBuilder {
    public void buildDough()   { pizza.setDough("cross"); }
    public void buildSauce()   { pizza.setSauce("mild"); }
    public void buildTopping() { pizza.setTopping("ham+pineapple"); }
 }
 
 /** "ConcreteBuilder" */
 class SpicyPizzaBuilder extends PizzaBuilder {
    public void buildDough()   { pizza.setDough("pan baked"); }
    public void buildSauce()   { pizza.setSauce("hot"); }
    public void buildTopping() { pizza.setTopping("pepperoni+salami"); }
 }
 
 
 /** "Director" */
 class Waiter {
    private PizzaBuilder pizzaBuilder;
 
    public void setPizzaBuilder(PizzaBuilder pb) { pizzaBuilder = pb; }
    public Pizza getPizza() { return pizzaBuilder.getPizza(); }
 
    public void constructPizza() {
       pizzaBuilder.createNewPizzaProduct();
       pizzaBuilder.buildDough();
       pizzaBuilder.buildSauce();
       pizzaBuilder.buildTopping();
    }
 }
 
 
 /** A customer ordering a pizza. */
 class BuilderExample {
    public static void main(String[] args) {
        Waiter waiter = new Waiter();
        PizzaBuilder hawaiianPizzaBuilder = new HawaiianPizzaBuilder();
        PizzaBuilder spicyPizzaBuilder = new SpicyPizzaBuilder();
 
        waiter.setPizzaBuilder( hawaiianPizzaBuilder );
        waiter.constructPizza();
 
        Pizza pizza = waiter.getPizza();
    }
 }