Exploring Advanced Language Features - Beginning Java 7 - page 295

• clone() isoverriddentopreventconstantsfrombeingclonedsothatthereis
evermorethanonecopyofaconstant;otherwise,constantscouldnotbecom-
pared via == .
• equals() isoverriddentocompareconstantsviatheirreferences—constants
with the same identities ( == ) must have the same contents ( equals() ), and
different identities imply different contents.
• finalize() is overridden to ensure that constants cannot be finalized.
• hashCode() is overridden because equals() is overridden.
• toString() is overridden to return the constant's name.
Exceptfor toString() ,alloftheoverridingmethodsaredeclared final sothat
they cannot be overridden in a subclass.
Enum also provides its own methods. These methods include the final com-
pareTo() , ( Enum implements Comparable ), getDeclaringClass() ,
name() , and ordinal() methods:
• compareTo() compares the current constant with the constant passed as an
argument to see which constant precedes the other constant in the enum, and
returnsavalueindicatingtheirorder.Thismethodmakesitpossibletosortan
array of unsorted constants.
• getDeclaringClass() returns the Class object corresponding to the
currentconstant'senum.Forexample,the Class objectfor Coin isreturned
whencalling Coin.PENNY.getDeclaringClass() for enum Coin {
PENNY, ICKEL, DIME, QUARTER } . Also, TempConversion is
returnedwhencalling TempConversion.C2F.getDeclaringClass()
for Listing 3-65 's TempConversion enum. The compareTo() method
uses Class 's getClass() methodand Enum 's getDeclaringClass()
methodtoensurethatonlyconstantsbelongingtothesameenumarecompared.
Otherwise, a ClassCastException is thrown. (I will discuss Class in
Chapter 4 . )
• name() returns the constant's name. Unless overridden to return something
more descriptive, toString() also returns the constant's name.
• ordinal() returnsazero-based ordinal ,anintegerthatidentifiestheposition
of the constant within the enum type. compareTo() compares ordinals.
Enum also provides the public static <T extends Enum<T>> T
valueOf(Class<T> enumType, String name) method for returning the
enum constant from the specified enum with the specified name: