Ordering enum values

Question

I was wondering if there is any way of ordering enum for different classes. If for example, I have a fixed group of chemicals which react in different ways to other chemical

Answer 1

You can put as many comparators in the enum as you like, see below example:

import java.util.Comparator;

public enum Day {
    MONDAY(1, 3),
    TUESDAY(2, 6),
    WEDNESDAY(3, 5),
    THURSDAY(4, 4),
    FRIDAY(5, 2),
    SATURDAY(6, 1),
    SUNDAY(0, 0);

    private final int calendarPosition;
    private final int workLevel;

    Day(int position, int level) {
      calendarPosition = position;
      workLevel = level;
    }

    int getCalendarPosition(){ return calendarPosition; }  
    int getWorkLevel() { return workLevel;  }

    public static Comparator calendarPositionComparator = new Comparator() {
      public int compare(Day d1, Day d2) {
        return d1.getCalendarPosition() - d2.getCalendarPosition();
      }
    };

    public static Comparator workLevelComparator = new Comparator() {
      public int compare(Day d1, Day d2) {
        // descending order, harder first
        return d2.getWorkLevel() - d1.getWorkLevel();
      }
    };
}

To see comparators in action:

import java.util.Arrays;
import java.util.Collections;
import java.util.List;

public class EnumDayTest
{
  public static void main (String[] args) {
     List allDays = Arrays.asList(Day.values());
     System.out.println("===\nListing days in order of calendar position:");
     Collections.sort(allDays, Day.calendarPositionComparator);
     showItems(allDays);
     System.out.println("===\nListing days in order of work level:");
     Collections.sort(allDays, Day.workLevelComparator);
     showItems(allDays);
  }

  public static void showItems(List days) {
    for (Day day : days) {
      System.out.println(day.name());
    }
  }
}