How to reverse lookup an enum from its values in Java?

Sometime, you need to lookup an enum from its value (may be a integer, string or other types). This reverse lookup can be easily implemented by using a static java.util.Map inside your enum class. For example,

import java.util.HashMap;
import java.util.Map;

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

     private static final Map lookup = 

			new HashMap();

     static {
         //Create reverse lookup hash map 
         for(Day d : Day.values())
             lookup.put(d.getDayValue(), d);
     }

     private int dayValue;

     private Day(int dayValue) {
          this.dayValue = dayValue;
     }

     public int getDayValue() { return dayValue; }

     public static Day get(int dayValue) { 

        //the reverse lookup by simply getting 
        //the value from the lookup HsahMap. 

          return lookup.get(dayValue); 
     }
}

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