Java如何通过枚举实现有限状态机

public enum JavaPlatformState {
  // 定义state
  OPEN{
    @Override void exit(JavaPlatformMachine pm){super.exit(pm);}
    
    @Override void valid(JavaPlatformMachine pm){
      this.exit(pm);
      if(pm.data.getValid_()){
        pm.state =STEP1;
      }else{
        NotFound();
        pm.state =OFF;
      }
      pm.state.entry(pm);
    }

    @Override
    void first(JavaPlatformMachine pm) {}

    @Override
    void businessLine(JavaPlatformMachine pm) {}

    @Override
    void district(JavaPlatformMachine pm) {}
  },
  STEP1{
    @Override void exit(JavaPlatformMachine pm){super.exit(pm);}

    @Override
    void valid(JavaPlatformMachine pm) {}

    @Override void first(JavaPlatformMachine pm){
      this.exit(pm);
      if(!pm.data.getFirst_()){
        pm.state =STEP2;
      }else{
        ReturnDimension();
        pm.state =OFF;
      }
      pm.state.entry(pm);
    }

    @Override
    void businessLine(JavaPlatformMachine pm) {}

    @Override
    void district(JavaPlatformMachine pm) {}
  },
  ...
  
  //状态模式 提取的接口 在常量实体类中实现抽象方法
  abstract void valid(JavaPlatformMachine pm);
  abstract void first(JavaPlatformMachine pm);
  abstract void businessLine(JavaPlatformMachine pm);
  abstract void district(JavaPlatformMachine pm); 
}

//状态机的各种动作action methode
  void entry(JavaPlatformMachine pm){System.out.println("→"+pm.state.name());}
  void exit(JavaPlatformMachine pm){System.out.println(pm.state.name()+"→ ");}
  
  void NotFound(){System.out.println("NotFound");}
  void ReturnDimension(){System.out.println("ReturnDimension");}
  void PreciseAdvertising(){System.out.println("PreciseAdvertising");}
  void Top9(){System.out.println("Top9");}

public class ContextData {
  private Boolean isValid_;//广告位是否有效
  private Boolean isFirst_;//是否第一次请求
  private Boolean isBusinessLine_;//是否属于业务线广告位
  private Boolean district_;//是否有地域
  ...
}

public class JavaPlatformMachine {
  ContextData data = new ContextData();
  JavaPlatformState state = JavaPlatformState.OPEN;
  //Action
  public void valid(){state.valid(this);}
  public void first(){state.first(this);}
  public void businessLine(){state.businessLine(this);}
  public void district(){state.district(this);}
}

JavaPlatformMachine pm = new JavaPlatformMachine();
  pm.data.setValid_(true);// 广告位是否有效
  pm.data.setFirst_(false);// 是否第一次请求
  pm.data.setBusinessLine_(true);//是否属于业务线广告位
  pm.data.setDistrict_(true);//是否有地域
  pm.valid();
  pm.first();
  pm.businessLine();
  pm.district();

OPEN→ 
→STEP1
STEP1→ 
→STEP2
STEP2→ 
→STEP3
STEP3→ 
Top9
→OFF