建造者模式

抽象建造者定义建造的零件方法和获取产品的方法，具体建造者实现这些方法。

导演角色主要调用具体建造者角色用以创建产品对象

产品角色是建造的最终产品，一般来说一个系统会有多于一个的产品类，而且这些产品类并不一定有共同的接口，可以完全是不相关联的。

下面依然以造车示例建造者模式：

public class BuilderDemo {
  static class Director {
    private Builder builder;

    public Car constructAccord() {
      builder = new AccordBuilder();
      builder.buildChassis();
      builder.buildEngine();
      builder.buildWheel();
      builder.buildTransmission();
      return builder.getProduct();
    }
  }

  static class Car {
    private String chassis;
    private String wheel;
    private String Engine;
    private String Transmission;

    public String toString() {
      StringBuilder sb = new StringBuilder();
      sb.append("发动机：" + this.getEngine()+"
");
      sb.append("轮胎：" + this.getWheel()+"
");
      sb.append("变速箱：" + this.getTransmission()+"
");
      sb.append("底盘：" + this.getChassis()+"
");
      return sb.toString();
    }

    public String getChassis() {
      return chassis;
    }

    public void setChassis(String chassis) {
      this.chassis = chassis;
    }

    public String getWheel() {
      return wheel;
    }

    public void setWheel(String wheel) {
      this.wheel = wheel;
    }

    public String getEngine() {
      return Engine;
    }

    public void setEngine(String engine) {
      Engine = engine;
    }

    public String getTransmission() {
      return Transmission;
    }

    public void setTransmission(String transmission) {
      Transmission = transmission;
    }
  }

  interface Builder {
    void buildChassis();

    void buildWheel();

    void buildEngine();

    void buildTransmission();

    Car getProduct();

  }

  static class AccordBuilder implements Builder {

    Car car = new Car();

    @Override
    public void buildChassis() {
      this.car.setChassis("好底盘");
    }

    @Override
    public void buildWheel() {
      this.car.setWheel("倍耐力轮胎");
    }

    @Override
    public void buildEngine() {
      this.car.setEngine("地球梦发动机");
    }

    @Override
    public void buildTransmission() {
      this.car.setTransmission("10AT变速箱");
    }

    @Override
    public Car getProduct() {
      return this.car;
    }
  }

  public static void main(String[] args) {
    Director director = new Director();
    Car accord = director.constructAccord();
    System.out.println("---生产出一辆雅阁---");
    System.out.println(accord.toString());
  }
}

建造者模式的导演者其实可以去除，如果只有一种构建的产品，那么其实也就不需要导演者这个角色了。

去掉导演者角色的建造者设计模式其实就是“模板方法设计模式”