Switch on Enum in Java

Question

Why can t you switch on an enum in Java  It seems simple enough to do and would make for some convenient code  Also this question could apply to String s  You can switch on a char  but not a String

User · Answer

You might be using the enums incorrectly in the switch cases. In comparison with the above example by CoolBeans.. you might be doing the following:

switch(day) {
    case Day.MONDAY:
        // Something..
        break;
    case Day.FRIDAY:
        // Something friday
        break;
}

Make sure that you use the actual enum values instead of EnumType.EnumValue

Eclipse points out this mistake though..

User · Answer

Actually you can use a switch statement with Strings in Java   unfortunately this is a new feature of Java 7  and most people are not using Java 7 yet because it s so new

User · Answer

Article on Programming Guide  Switch on enum    enum MyEnum   CONST ONE  CONST TWO    class Test           public static void main String   args                MyEnum e   MyEnum CONST ONE               switch  e                    case CONST ONE  System out println 1   break                  case CONST TWO  System out println 2   break                                  Switches for strings are implemented in Java 7

User · Answer

You actually can switch on enums  but you can t switch on Strings until Java 7  You might consider using polymorphic method dispatch with Java enums rather than an explicit switch  Note that enums are objects in Java  not just symbols for ints like they are in C C    You can have a method on an enum type  then instead of writing a switch  just call the method - one line of code  done   enum MyEnum       SOME ENUM CONSTANT            Override         public void method                 System out println  first enum constant behavior                          ANOTHER ENUM CONSTANT            Override         public void method                 System out println  second enum constant behavior                         note the semi-colon after the final constant  not just a comma      public abstract void method       could also be in an interface that MyEnum implements    void aMethodSomewhere final MyEnum e        doSomeStuff        e method       here is where the switch would be  now it s one line of code      doSomeOtherStuff

User · Answer

First  you can switch on an enum in Java  I m guessing you intended to say you can   t  but you can  chars have a set range of values  so it s easy to compare  Strings can be anything   A switch statement is usually implemented as a jump table  branch table  in the underlying compilation  which is only possible with a finite set of values  C  can switch on strings  but it causes a performance decrease because a jump table cannot be used   Java 7 and later supports String switches with the same characteristics

User · Answer

You definitely can switch on enums  An example posted from the Java tutorials   public enum Day       SUNDAY  MONDAY  TUESDAY  WEDNESDAY       THURSDAY  FRIDAY  SATURDAY     public class EnumTest       Day day       public EnumTest Day day            this day   day             public void tellItLikeItIs              switch  day                case MONDAY                   System out println  Mondays are bad                     break               case FRIDAY                   System out println  Fridays are better                     break               case SATURDAY              case SUNDAY                   System out println  Weekends are best                     break               default                  System out println  Midweek days are so-so                     break

[java] Switch on Enum in Java

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