use enum as generic parameter-CodePudding

I have an enum day

public enum DAY { SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY}

I want to create a generic interface so that for each day I want to have a different implementation

public interface DayLogic<T>
{
  void doLogic();
}

I want <T> to be a value of DAY enum for example

public class WednesdayLogic implements DayLogic<DAY.WEDNESDAY>
{
   @Override
   public void doLogic()
   {}    
}

is it possible or is there any alternate flow to do so?

CodePudding user response：

Since there are already answers to your original question, here's what you can do that should fit your use case: since an enum is just a (restricted) class, it can implement an interface, which looks like what you need:

public enum DAY implements DayLogic { 
 SUNDAY {
  public void doLogic() {
   // sunday logic implementation
  }
 }, 
 MONDAY{
  public void doLogic() {
   // monday logic implementation
  }
 }, 
 // ...
}

You can then use it like

DAY day = decideDay();
day.doLogic();

If you don't like the individual values having the method (I don't), you can do something like

public enum DAY implements DayLogic {
 SUNDAY(new SundayLogic()),
 MONDAY(new MondayLogic()),
 // ...
 ;

 private DayLogic logicDelegate; // or Runnable, it's the same signature

 private DAY(DayLogic logic) {
  logicDelegate = logic;
 }

 public doLogic() {
  logicDelegate.run();
 }
}

CodePudding user response：

Looks like you can achieve this concept by:

public enum DAY
{
    SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY
}

Day Logic interface and Factory initializer

public interface DayLogic
{
    void doLogic();

    public static class Factory
    {
        public DayLogic getDayLogic(DAY day)
        {
            if (DAY.WEDNESDAY.equals(day))
            {
                return new WednesdayLogic();
            }
            // ...
            return null;
        }
    }
}

WednesdayLogic Class:

public class WednesdayLogic implements DayLogic
{
    final DAY day = DAY.WEDNESDAY;

    @Override
    public void doLogic()
    {
        // TODO Auto-generated method stub

    }
}

Problem is that Enum Day is a value, not a class.

CodePudding user response：

The answer from daniu is one option: the enum can implement an interface, and you do all in the interface. Especially using a constructor with DayLogic is nice.

Often that DayLogic is a later, uncoupled phenomenon. In that case use an EnumMap from the enum to your logic.

public class Dayly {
    private final Map<Day, DayLogic> logicMap = new EnumMap<>(Day.class);

    public void putLogic(Day day, DayLogic logic) {
        logicMap.put(day, logic);
    }
    ...
}