Enums vs Constants

Suppose you use constant strings (or int values - the same goes for them):

// Constants for player types
public static final String ARCHER = "Archer";
public static final String WARRIOR = "Warrior";

// Constants for genders
public static final String MALE = "Male";
public static final String FEMALE = "Female";

then you end up not really knowing the type of your data - leading to potentially incorrect code:

String playerType = Constants.MALE;

If you use enums, that would end up as:

// Compile-time error - incompatible types!
PlayerType playerType = Gender.MALE;

Likewise, enums give a restricted set of values:

String playerType = "Fred"; // Hang on, that's not one we know about...

vs

PlayerType playerType = "Fred"; // Nope, that doesn't work. Bang!

Additionally, enums in Java can have more information associated with them, and can also have behaviour. Much better all round.