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 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package javax.print.attribute;

import java.io.InvalidObjectException;
import java.io.ObjectStreamException;
import java.io.Serializable;

/**
 * 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:
 * <PRE>
 * 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;
 * }
 * }
 * </PRE>
 * You can then write code that uses the <CODE>==</CODE> and <CODE>!=</CODE>
 * operators to test enumeration values; for example:
 * <PRE>
 * Bach theComposer;
 * . . .
 * if (theComposer == Bach.JOHANN_SEBASTIAN) {
 * System.out.println ("The greatest composer of all time!");
 * }
 * </PRE>
 * The <CODE>equals()</CODE> method for an enumeration class just does a test
 * for identical objects (<CODE>==</CODE>).
 * <P>
 * You can convert an enumeration value to a string by calling {@link
 * #toString() toString()}. The string is obtained from a table
 * supplied by the enumeration class.
 * <P>
 * 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 {@link #getValue()
 * getValue()}. An enumeration value's integer value is established
 * when it is constructed (see {@link #EnumSyntax(int)
 * 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.
 * <P>
 * 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 <CODE>==</CODE>, <CODE>!=</CODE>, <CODE>equals()</CODE>, and
 * <CODE>toString()</CODE> 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.
 * <P>
 *
 * @author David Mendenhall
 * @author Alan Kaminsky
 */
public abstract class EnumSyntax implements Serializable, Cloneable {

 private static final long serialVersionUID = -2739521845085831642L;

 /**
 * This enumeration value's integer value.
 * @serial
 */
 private int value;

 /**
 * Construct a new enumeration value with the given integer value.
 *
 * @param value Integer value.
 */
 protected EnumSyntax(int value) {
 this.value = value;
 }

 /**
 * Returns this enumeration value's integer value.
 * @return the value
 */
 public int getValue() {
 return value;
 }

 /**
 * Returns a clone of this enumeration value, which to preserve the
 * semantics of enumeration values is the same object as this enumeration
 * value.
 */
 public Object clone() {
 return this;
 }

 /**
 * Returns a hash code value for this enumeration value. The hash code is
 * just this enumeration value's integer value.
 */
 public int hashCode() {
 return value;
 }

 /**
 * Returns a string value corresponding to this enumeration value.
 */
 public String toString() {

 String[] theTable = getStringTable();
 int theIndex = value - getOffset();
 return
 theTable != null && theIndex >= 0 && theIndex < theTable.length ?
 theTable[theIndex] :
 Integer.toString (value);
 }

 /**
 * During object input, convert this deserialized enumeration instance to
 * the proper enumeration value defined in the enumeration attribute class.
 *
 * @return The enumeration singleton value stored at index
 * <I>i</I>-<I>L</I> in the enumeration value table returned by
 * {@link #getEnumValueTable() getEnumValueTable()},
 * where <I>i</I> is this enumeration value's integer value and
 * <I>L</I> is the value returned by {@link #getOffset()
 * getOffset()}.
 *
 * @throws ObjectStreamException if the stream can't be deserialised
 * @throws 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: {@link
 * java.io.InvalidObjectException InvalidObjectException} is a subclass
 * of {@link java.io.ObjectStreamException ObjectStreamException}, which
 * <CODE>readResolve()</CODE> is declared to throw.)
 */
 protected Object readResolve() throws ObjectStreamException {

 EnumSyntax[] theTable = getEnumValueTable();

 if (theTable == null) {
 throw new InvalidObjectException(
 "Null enumeration value table for class " +
 getClass());
 }

 int theOffset = getOffset();
 int theIndex = value - theOffset;

 if (0 > theIndex || theIndex >= theTable.length) {
 throw new InvalidObjectException
 ("Integer value = " + value + " not in valid range " +
 theOffset + ".." + (theOffset + theTable.length - 1) +
 "for class " + getClass());
 }

 EnumSyntax result = theTable[theIndex];
 if (result == null) {
 throw new InvalidObjectException
 ("No enumeration value for integer value = " +
 value + "for class " + getClass());
 }
 return result;
 }

 // Hidden operations to be implemented in a subclass.

 /**
 * Returns the string table for this enumeration value's enumeration class.
 * The enumeration class's integer values are assumed to lie in the range
 * <I>L</I>..<I>L</I>+<I>N</I>-1, where <I>L</I> is the value returned by
 * {@link #getOffset() getOffset()} and <I>N</I> is the length
 * of the string table. The element in the string table at index
 * <I>i</I>-<I>L</I> is the value returned by {@link #toString()
 * toString()} for the enumeration value whose integer value
 * is <I>i</I>. If an integer within the above range is not used by any
 * enumeration value, leave the corresponding table element null.
 * <P>
 * 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 {@link
 * #toString() toString()} method, the base class {@link
 * #toString() toString()} method will return just a string
 * representation of this enumeration value's integer value.
 * @return the string table
 */
 protected String[] getStringTable() {
 return null;
 }

 /**
 * 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 <I>L</I>..<I>L</I>+<I>N</I>-1, where <I>L</I> is the
 * value returned by {@link #getOffset() getOffset()} and
 * <I>N</I> is the length of the enumeration value table. The element in the
 * enumeration value table at index <I>i</I>-<I>L</I> is the enumeration
 * value object whose integer value is <I>i</I>; the {@link #readResolve()
 * 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.
 * <P>
 * 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 {@link #readResolve() readResolve()} method, the base
 * class {@link #readResolve() readResolve()} method will throw
 * an exception whenever an enumeration instance is deserialized from an
 * object input stream.
 * @return the value table
 */
 protected EnumSyntax[] getEnumValueTable() {
 return null;
 }

 /**
 * Returns the lowest integer value used by this enumeration value's
 * enumeration class.
 * <P>
 * 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.
 * @return the offset of the lowest enumeration value.
 */
 protected int getOffset() {
 return 0;
 }

}