参考：http://blog.csdn.net/lovelion/article/details/17517213 

//电影票类：环境类  class MovieTicket {      private double price;      private Discount discount; //维持一个对抽象折扣类的引用        public void setPrice(double price) {          this.price = price;      }        //注入一个折扣类对象      public void setDiscount(Discount discount) {          this.discount = discount;      }        public double getPrice() {          //调用折扣类的折扣价计算方法          return discount.calculate(this.price);      }  }    //折扣类：抽象策略类  interface Discount {      public double calculate(double price);  }    //学生票折扣类：具体策略类  class StudentDiscount implements Discount {      public double calculate(double price) {          System.out.println("学生票：");          return price * 0.8;      }  }     //儿童票折扣类：具体策略类  class ChildrenDiscount implements Discount {      public double calculate(double price) {          System.out.println("儿童票：");          return price - 10;      }  }     //VIP会员票折扣类：具体策略类  class VIPDiscount implements Discount {      public double calculate(double price) {          System.out.println("VIP票：");          System.out.println("增加积分！");          return price * 0.5;      }  }