- All Implemented Interfaces:
Serializable
,Cloneable
- Direct Known Subclasses:
Chromaticity
,ColorSupported
,Compression
,DialogTypeSelection
,Fidelity
,Finishings
,JobSheets
,JobState
,JobStateReason
,Media
,MultipleDocumentHandling
,OrientationRequested
,PDLOverrideSupported
,PresentationDirection
,PrinterIsAcceptingJobs
,PrinterState
,PrinterStateReason
,PrintQuality
,ReferenceUriSchemesSupported
,Severity
,SheetCollate
,Sides
EnumSyntax
is an abstract base class providing the common
implementation of all "type safe enumeration" objects. An enumeration class
(which extends class EnumSyntax
) provides a group of enumeration
values (objects) that are singleton instances of the enumeration class; for
example:
public class Bach extends EnumSyntax { public static final Bach JOHANN_SEBASTIAN = new Bach(0); public static final Bach WILHELM_FRIEDEMANN = new Bach(1); public static final Bach CARL_PHILIP_EMMANUEL = new Bach(2); public static final Bach JOHANN_CHRISTIAN = new Bach(3); public static final Bach P_D_Q = new Bach(4); private static final String[] stringTable = { "Johann Sebastian Bach", "Wilhelm Friedemann Bach", "Carl Philip Emmanuel Bach", "Johann Christian Bach", "P.D.Q. Bach" }; protected String[] getStringTable() { return stringTable; } private static final Bach[] enumValueTable = { JOHANN_SEBASTIAN, WILHELM_FRIEDEMANN, CARL_PHILIP_EMMANUEL, JOHANN_CHRISTIAN, P_D_Q }; protected EnumSyntax[] getEnumValueTable() { return enumValueTable; } }You can then write code that uses the
==
and !=
operators to
test enumeration values; for example:
Bach theComposer; . . . if (theComposer == Bach.JOHANN_SEBASTIAN) { System.out.println ("The greatest composer of all time!"); }The
equals()
method for an enumeration class just does a test for
identical objects (==
).
You can convert an enumeration value to a string by calling
toString()
. The string is obtained from a table supplied
by the enumeration class.
Under the hood, an enumeration value is just an integer, a different integer
for each enumeration value within an enumeration class. You can get an
enumeration value's integer value by calling getValue()
.
An enumeration value's integer value is established when it is constructed
(see EnumSyntax(int)
). Since the constructor is
protected, the only possible enumeration values are the singleton objects
declared in the enumeration class; additional enumeration values cannot be
created at run time.
You can define a subclass of an enumeration class that extends it with
additional enumeration values. The subclass's enumeration values' integer
values need not be distinct from the superclass's enumeration values' integer
values; the ==
, !=
, equals()
, and toString()
methods will still work properly even if the subclass uses some of the same
integer values as the superclass. However, the application in which the
enumeration class and subclass are used may need to have distinct integer
values in the superclass and subclass.
- See Also:
-
Constructor Summary
ModifierConstructorDescriptionprotected
EnumSyntax
(int value) Construct a new enumeration value with the given integer value. -
Method Summary
Modifier and TypeMethodDescriptionclone()
Returns a clone of this enumeration value, which to preserve the semantics of enumeration values is the same object as this enumeration value.protected EnumSyntax[]
Returns the enumeration value table for this enumeration value's enumeration class.protected int
Returns the lowest integer value used by this enumeration value's enumeration class.protected String[]
Returns the string table for this enumeration value's enumeration class.int
getValue()
Returns this enumeration value's integer value.int
hashCode()
Returns a hash code value for this enumeration value.protected Object
During object input, convert this deserialized enumeration instance to the proper enumeration value defined in the enumeration attribute class.toString()
Returns a string value corresponding to this enumeration value.
-
Constructor Details
-
EnumSyntax
protected EnumSyntax(int value) Construct a new enumeration value with the given integer value.- Parameters:
value
- Integer value
-
-
Method Details
-
getValue
public int getValue()Returns this enumeration value's integer value.- Returns:
- the value
-
clone
-
hashCode
-
toString
-
readResolve
During object input, convert this deserialized enumeration instance to the proper enumeration value defined in the enumeration attribute class.- Returns:
- The enumeration singleton value stored at index i-L
in the enumeration value table returned by
getEnumValueTable()
, where i is this enumeration value's integer value and L is the value returned bygetOffset()
- Throws:
ObjectStreamException
- if the stream can't be deserialisedInvalidObjectException
- if the enumeration value table isnull
, this enumeration value's integer value does not correspond to an element in the enumeration value table, or the corresponding element in the enumeration value table isnull
. (Note:InvalidObjectException
is a subclass ofObjectStreamException
, whichreadResolve()
is declared to throw.)
-
getStringTable
Returns the string table for this enumeration value's enumeration class. The enumeration class's integer values are assumed to lie in the range L..L+N-1, where L is the value returned bygetOffset()
and N is the length of the string table. The element in the string table at index i-L is the value returned bytoString()
for the enumeration value whose integer value is i. If an integer within the above range is not used by any enumeration value, leave the corresponding table elementnull
.The default implementation returns
null
. If the enumeration class (a subclass of classEnumSyntax
) does not override this method to return anon-null
string table, and the subclass does not override thetoString()
method, the base classtoString()
method will return just a string representation of this enumeration value's integer value.- Returns:
- the string table
-
getEnumValueTable
Returns the enumeration value table for this enumeration value's enumeration class. The enumeration class's integer values are assumed to lie in the range L..L+N-1, where L is the value returned bygetOffset()
and N is the length of the enumeration value table. The element in the enumeration value table at index i-L is the enumeration value object whose integer value is i; thereadResolve()
method needs this to preserve singleton semantics during deserialization of an enumeration instance. If an integer within the above range is not used by any enumeration value, leave the corresponding table elementnull
.The default implementation returns
null
. If the enumeration class (a subclass of class EnumSyntax) does not override this method to return anon-null
enumeration value table, and the subclass does not override thereadResolve()
method, the base classreadResolve()
method will throw an exception whenever an enumeration instance is deserialized from an object input stream.- Returns:
- the value table
-
getOffset
protected int getOffset()Returns the lowest integer value used by this enumeration value's enumeration class.The default implementation returns 0. If the enumeration class (a subclass of class
EnumSyntax
) uses integer values starting at other than 0, override this method in the subclass.- Returns:
- the offset of the lowest enumeration value
-