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java.lang.Objectjavax.print.attribute.EnumSyntax
public abstract class EnumSyntax
Disabled: no SafeJ information.
Class 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
. The string is obtained from a table
supplied by the enumeration class.
toString()
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
. An enumeration value's integer value is established
when it is constructed (see getValue()
). 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.
EnumSyntax(int)
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.
Constructor Summary | |
---|---|
protected |
EnumSyntax(int value)
Construct a new enumeration value with the given integer value. |
Method Summary | |
---|---|
Object |
clone()
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[] |
getEnumValueTable()
Returns the enumeration value table for this enumeration value's enumeration class. |
protected int |
getOffset()
Returns the lowest integer value used by this enumeration value's enumeration class. |
protected String[] |
getStringTable()
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 |
readResolve()
During object input, convert this deserialized enumeration instance to the proper enumeration value defined in the enumeration attribute class. |
String |
toString()
Returns a string value corresponding to this enumeration value. |
Methods inherited from class java.lang.Object |
---|
equals, finalize, getClass, notify, notifyAll, wait, wait, wait |
Constructor Detail |
---|
protected EnumSyntax(int value)
value
- Integer value.Method Detail |
---|
public int getValue()
public Object clone()
clone
in class Object
Cloneable
public int hashCode()
hashCode
in class Object
Object.equals(java.lang.Object)
,
System.identityHashCode(java.lang.Object)
public String toString()
toString
in class Object
protected Object readResolve() throws ObjectStreamException
getEnumValueTable()
,
where i is this enumeration value's integer value and
L is the value returned by getOffset()
.
ObjectStreamException
- if the stream can't be deserialised
InvalidObjectException
- Thrown if the enumeration value table is null, 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 is null. (Note: InvalidObjectException
is a subclass
of ObjectStreamException
, which
readResolve()
is declared to throw.)protected String[] getStringTable()
getOffset()
and N is the length
of the string table. The element in the string table at index
i-L is the value returned by toString()
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 element null.
The default implementation returns null. If the enumeration class (a
subclass of class EnumSyntax) does not override this method to return a
non-null string table, and the subclass does not override the
method, the base class toString()
method will return just a string
representation of this enumeration value's integer value.
toString()
protected EnumSyntax[] getEnumValueTable()
getOffset()
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; the readResolve()
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 element null.
The default implementation returns null. If the enumeration class (a
subclass of class EnumSyntax) does not override this method to return
a non-null enumeration value table, and the subclass does not override
the
method, the base
class readResolve()
method will throw
an exception whenever an enumeration instance is deserialized from an
object input stream.
readResolve()
protected int getOffset()
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.
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