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Rework Functional Enums to work on JDK1.2 

bug 19030


git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/lang/trunk@137570 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Stephen Colebourne 2003-08-04 23:52:27 +00:00
parent cf7f46f654
commit 8b1992ee2f
3 changed files with 136 additions and 71 deletions
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137
src/java/org/apache/commons/lang/enum/Enum.java
View File

@ -75,9 +75,12 @@ import org.apache.commons.lang.StringUtils;
* however that a more robust type-safe class-based solution can be designed. This
* class follows the basic Java type-safe enumeration pattern.</p>
*
* <p><em>NOTE:</em>Due to the way in which Java ClassLoaders work, comparing Enum objects
* should always be done using the equals() method, not ==. The equals() method will
* try == first so in most cases the effect is the same.</p>
* <p><em>NOTE:</em>Due to the way in which Java ClassLoaders work, comparing
* Enum objects should always be done using <code>equals()</code>, not <code>==</code>.
* The equals() method will try == first so in most cases the effect is the same.</p>
*
* <p>Of course, if you actually want (or don't mind) Enums in different class
* loaders being non-equal, then you can use <code>==</code>.</p>
*
* <h4>Simple Enums</h4>
*
@ -125,7 +128,7 @@ import org.apache.commons.lang.StringUtils;
* superclass and subclass.</p>
*
* <pre>
* public class ExtraColorEnum extends ColorEnum {
* public final class ExtraColorEnum extends ColorEnum {
* // NOTE: Color enum declared above is final, change that to get this
* // example to compile.
* public static final ColorEnum YELLOW = new ExtraColorEnum("Yellow");
@ -159,24 +162,31 @@ import org.apache.commons.lang.StringUtils;
*
* <h4>Functional Enums</h4>
*
* <p>The enums can have functionality by using anonymous inner classes
* [Effective Java, Bloch01]:</p>
* <p>The enums can have functionality by defining subclasses and
* changing the <code>super()</code> call:</p>
*
* <pre>
* public abstract class OperationEnum extends Enum {
* public static final OperationEnum PLUS = new OperationEnum("Plus") {
* public double eval(double a, double b) {
* public static final OperationEnum PLUS = new PlusOperation();
* private static final class PlusOperation extends OperationEnum {
* private PlusOperation() {
* super("Plus");
* }
* public int eval(int a, int b) {
* return (a + b);
* }
* };
* public static final OperationEnum MINUS = new OperationEnum("Minus") {
* public double eval(double a, double b) {
* }
* public static final OperationEnum MINUS = new MinusOperation();
* private static final class MinusOperation extends OperationEnum {
* private MinusOperation() {
* super("Minus");
* }
* public int eval(int a, int b) {
* return (a - b);
* }
* };
* }
*
* private OperationEnum(String color) {
* super(color);
* super(color, OperationEnum.class); // NOTE: super() changed!
* }
*
* public abstract double eval(double a, double b);
@ -198,18 +208,20 @@ import org.apache.commons.lang.StringUtils;
* }
* }
* </pre>
* <p>The code above will work on JDK 1.2. If JDK1.3 and later is used,
* the subclasses may be defined as anonymous.</p>
*
* @author Apache Avalon project
* @author Stephen Colebourne
* @author Chris Webb
* @author Mike Bowler
* @since 1.0
* @version $Id: Enum.java,v 1.17 2003/07/30 23:17:23 scolebourne Exp $
* @version $Id: Enum.java,v 1.18 2003/08/04 23:52:27 scolebourne Exp $
*/
public abstract class Enum implements Comparable, Serializable {
/** Lang version 1.0.1 serial compatability */
static final long serialVersionUID = -487045951170455942L;
private static final long serialVersionUID = -487045951170455942L;
// After discussion, the default size for HashMaps is used, as the
// sizing algorithm changes across the JDK versions
@ -225,6 +237,10 @@ public abstract class Enum implements Comparable, Serializable {
* The string representation of the Enum.
*/
private final String iName;
/**
* The Enum class.
*/
private final Class iEnumClass;
/**
* The hashcode representation of the Enum.
*/
@ -264,15 +280,53 @@ public abstract class Enum implements Comparable, Serializable {
*/
protected Enum(String name) {
super();
init(name, getClass());
iName = name;
iEnumClass = getClass();
iHashCode = 7 + iEnumClass.hashCode() + 3 * name.hashCode();
// cannot create toString here as subclasses may want to include other data
}
/**
* <p>Constructor to add a new named item to the enumeration.</p>
*
* <p>This constructor is used when a subclass wants to allow further
* subclasses to add values to the enumeration. The class specifies
* which class they are all to be tied to.</p>
*
* @param name the name of the enum object,
* must not be empty or <code>null</code>
* @param enumClass the enum class,
* must not be null and must be this class or a superclass
* @throws IllegalArgumentException if the name is <code>null</code>
* or an empty string
* @throws IllegalArgumentException if the enumClass is <code>null</code>
* or invalid
*/
protected Enum(String name, Class enumClass) {
super();
init(name, enumClass);
iName = name;
iEnumClass = enumClass;
iHashCode = 7 + enumClass.hashCode() + 3 * name.hashCode();
// cannot create toString here as subclasses may want to include other data
}
/**
* Initializes the enumeration.
*
* @param name the enum name
* @param enumClass the enum class
* @throws IllegalArgumentException if the name is null or empty
* @throws IllegalArgumentException if the enumClass is null or invalid
*/
private void init(String name, Class enumClass) {
if (StringUtils.isEmpty(name)) {
throw new IllegalArgumentException("The Enum name must not be empty or null");
}
iName = name;
Class enumClass = Enum.getEnumClass(getClass());
Entry entry = (Entry) cEnumClasses.get(enumClass);
if (entry == null) {
entry = createEntry(getClass());
entry = createEntry(enumClass);
cEnumClasses.put(enumClass, entry);
}
if (entry.map.containsKey(name)) {
@ -280,9 +334,6 @@ public abstract class Enum implements Comparable, Serializable {
}
entry.map.put(name, this);
entry.list.add(this);
iHashCode = 7 + enumClass.hashCode() + 3 * name.hashCode();
// cannot create toString here as subclasses may want to include other data
}
/**
@ -292,7 +343,7 @@ public abstract class Enum implements Comparable, Serializable {
* @return the resolved object
*/
protected Object readResolve() {
Entry entry = (Entry) cEnumClasses.get(Enum.getEnumClass(getClass()));
Entry entry = (Entry) cEnumClasses.get(iEnumClass);
if (entry == null) {
return null;
}
@ -422,29 +473,6 @@ public abstract class Enum implements Comparable, Serializable {
return entry;
}
/**
* <p>Convert a class to the actual common enum class.</p>
*
* <p>This accounts for anonymous inner classes.</p>
*
* @param cls the class to get the name for
* @return the class name
*/
protected static Class getEnumClass(Class cls) {
String className = cls.getName();
int index = className.lastIndexOf('$');
if (index > -1) {
// is it an anonymous inner class?
String inner = className.substring(index + 1);
if (inner.length() > 0 &&
inner.charAt(0) >= '0' &&
inner.charAt(0) < '9') {
return cls.getSuperclass();
}
}
return cls;
}
//-----------------------------------------------------------------------
/**
* <p>Retrieve the name of this Enum item, set in the constructor.</p>
@ -455,6 +483,18 @@ public abstract class Enum implements Comparable, Serializable {
return iName;
}
/**
* <p>Retrieves the Class of this Enum item, set in the constructor.</p>
*
* <p>This is normally the same as <code>getClass()</code>, but for
* advanced Enums may be different.</p>
*
* @return the <code>String</code> name of this Enum item
*/
public final Class getEnumClass() {
return iEnumClass;
}
/**
* <p>Tests for equality.</p>
*
@ -473,7 +513,7 @@ public abstract class Enum implements Comparable, Serializable {
} else if (other.getClass() == this.getClass()) {
// shouldn't happen, but...
return iName.equals(((Enum) other).iName);
} else if (getEnumClass(other.getClass()).getName().equals(getEnumClass(this.getClass()).getName())) {
} else if (((Enum) other).iEnumClass.getName().equals(iEnumClass.getName())) {
// different classloaders
try {
// try to avoid reflection
@ -537,8 +577,7 @@ public abstract class Enum implements Comparable, Serializable {
*/
public String toString() {
if (iToString == null) {
Class cls = Enum.getEnumClass(getClass());
String shortName = ClassUtils.getShortClassName(cls);
String shortName = ClassUtils.getShortClassName(iEnumClass);
iToString = shortName + "[" + getName() + "]";
}
return iToString;

23
src/java/org/apache/commons/lang/enum/ValuedEnum.java
View File

@ -133,12 +133,12 @@ import org.apache.commons.lang.ClassUtils;
* @author Apache Avalon project
* @author Stephen Colebourne
* @since 1.0
* @version $Id: ValuedEnum.java,v 1.10 2003/07/30 23:17:23 scolebourne Exp $
* @version $Id: ValuedEnum.java,v 1.11 2003/08/04 23:52:27 scolebourne Exp $
*/
public abstract class ValuedEnum extends Enum {
/** Lang version 1.0.1 serial compatability */
static final long serialVersionUID = -7129650521543789085L;
private static final long serialVersionUID = -7129650521543789085L;
/**
* The value contained in enum.
@ -148,14 +148,26 @@ public abstract class ValuedEnum extends Enum {
/**
* Constructor for enum item.
*
* @param name the name of enum item.
* @param value the value of enum item.
* @param name the name of enum item
* @param value the value of enum item
*/
protected ValuedEnum(String name, int value) {
super(name);
iValue = value;
}
/**
* Constructor for enum item.
*
* @param name the name of enum item
* @param enumClass the enum class
* @param value the value of enum item
*/
protected ValuedEnum(String name, Class enumClass, int value) {
super(name, enumClass);
iValue = value;
}
/**
* <p>Gets an <code>Enum</code> object by class and value.</p>
*
@ -217,8 +229,7 @@ public abstract class ValuedEnum extends Enum {
*/
public String toString() {
if (iToString == null) {
Class cls = Enum.getEnumClass(getClass());
String shortName = ClassUtils.getShortClassName(cls);
String shortName = ClassUtils.getShortClassName(getEnumClass());
iToString = shortName + "[" + getName() + "=" + getValue() + "]";
}
return iToString;

47
src/test/org/apache/commons/lang/enum/OperationEnum.java
View File

@ -61,27 +61,42 @@ import java.util.Map;
* Operator enumeration.
*
* @author Stephen Colebourne
* @version $Id: OperationEnum.java,v 1.3 2003/08/02 18:38:36 scolebourne Exp $
* @version $Id: OperationEnum.java,v 1.4 2003/08/04 23:52:27 scolebourne Exp $
*/
public abstract class OperationEnum extends Enum {
public static final OperationEnum PLUS;
public static final OperationEnum MINUS;
static {
// Get around JDK Linux bug
PLUS = new OperationEnum("Plus") {
public int eval(int a, int b) {
return (a + b);
}
};
MINUS = new OperationEnum("Minus") {
public int eval(int a, int b) {
return (a - b);
}
};
// This syntax works for JDK 1.3 and upwards:
// public static final OperationEnum PLUS = new OperationEnum("Plus") {
// public int eval(int a, int b) {
// return (a + b);
// }
// };
// public static final OperationEnum MINUS = new OperationEnum("Minus") {
// public int eval(int a, int b) {
// return (a - b);
// }
// };
// This syntax works for JDK 1.2 and upwards:
public static final OperationEnum PLUS = new PlusOperation();
private static class PlusOperation extends OperationEnum {
private PlusOperation() {
super("Plus");
}
public int eval(int a, int b) {
return (a + b);
}
}
public static final OperationEnum MINUS = new MinusOperation();
private static class MinusOperation extends OperationEnum {
private MinusOperation() {
super("Minus");
}
public int eval(int a, int b) {
return (a - b);
}
}
private OperationEnum(String name) {
super(name);
super(name, OperationEnum.class);
}
public abstract int eval(int a, int b);