原来方式实现类似枚举                                                         新方法enum对照

public abstract class WeekDay{                                           public class EnumAbstract{
    private WeekDay(){}                                                                  public static void main(String[] args){
                                                                                                               TrafficLamp tl = TrafficLamp.RED;
 public abstract WeekDay nextDay();                                                        System.out.println(tl); 

    public final static WeekDay SUN = new WeekDay(){          }

           public WeekDay nextDay(){                                               public enum TrafficLamp{
              return MON;                                                                            RED(30){
           }                                                                                                      public TrafficLamp nextLamp(){
    };                                                                                                                  return GREEN;

    public final static WeekDay MON = new WeekDay(){                   }
    
           public WeekDay nextDay(){                                                      },GREEN(45){                         
              return SUN;                                                                                   public TrafficLamp nextLamp(){
           }                                                                                                               return YELLOW;
    };                                                                                                                 }
                                                                                                                  },YELLOW(5){
    public String toString(){                                                                          public TrafficLamp nextLamp(){
       return this==SUN?"SUN":"MON";                                                          return RED;
    }                                                                                                                   }
}                                                                                                                  };
                                                                                                             public abstract TrafficLamp nextLamp();

                                                                                                                  private int time;
                                                                                                                      private TrafficLamp(int time){

                                                                                                                               this.time = time;

                                                                                                                       }
                                                                                                              }

                                                                                                         }