Class ValuedEnum
- All Implemented Interfaces:
Serializable
,Comparable
Abstract superclass for type-safe enums with integer values suitable
for use in switch
statements.
NOTE: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.
To use this class, it must be subclassed. For example:
public final class JavaVersionEnum extends ValuedEnum { //standard enums for version of JVM public static final int JAVA1_0_VALUE = 100; public static final int JAVA1_1_VALUE = 110; public static final int JAVA1_2_VALUE = 120; public static final int JAVA1_3_VALUE = 130; public static final JavaVersionEnum JAVA1_0 = new JavaVersionEnum( "Java 1.0", JAVA1_0_VALUE ); public static final JavaVersionEnum JAVA1_1 = new JavaVersionEnum( "Java 1.1", JAVA1_1_VALUE ); public static final JavaVersionEnum JAVA1_2 = new JavaVersionEnum( "Java 1.2", JAVA1_2_VALUE ); public static final JavaVersionEnum JAVA1_3 = new JavaVersionEnum( "Java 1.3", JAVA1_3_VALUE ); private JavaVersionEnum(String name, int value) { super( name, value ); } public static JavaVersionEnum getEnum(String javaVersion) { return (JavaVersionEnum) getEnum(JavaVersionEnum.class, javaVersion); } public static JavaVersionEnum getEnum(int javaVersion) { return (JavaVersionEnum) getEnum(JavaVersionEnum.class, javaVersion); } public static Map getEnumMap() { return getEnumMap(JavaVersionEnum.class); } public static List getEnumList() { return getEnumList(JavaVersionEnum.class); } public static Iterator iterator() { return iterator(JavaVersionEnum.class); } }
NOTE:These are declared final
, so compilers may
inline the code. Ensure you recompile everything when using final.
The above class could then be used as follows:
public void doSomething(JavaVersionEnum ver) { switch (ver.getValue()) { case JAVA1_0_VALUE: // ... break; case JAVA1_1_VALUE: // ... break; //... } }
As shown, each enum has a name and a value. These can be accessed using
getName
and getValue
.
NOTE: Because the switch is ultimately sitting on top of an int, the example above is not type-safe. That is, there is nothing that checks that JAVA1_0_VALUE is a legal constant for JavaVersionEnum.
The getEnum
and iterator
methods are recommended.
Unfortunately, Java restrictions require these to be coded as shown in each subclass.
An alternative choice is to use the EnumUtils
class.
- Since:
- 2.1 (class existed in enum package from v1.0)
- Version:
- $Id: ValuedEnum.java 905636 2010-02-02 14:03:32Z niallp $
- See Also:
-
Field Summary
-
Constructor Summary
ConstructorsModifierConstructorDescriptionprotected
ValuedEnum
(String name, int value) Constructor for enum item. -
Method Summary
Methods inherited from class org.apache.commons.lang.enums.Enum
equals, getEnum, getEnumClass, getEnumList, getEnumMap, getName, hashCode, iterator, readResolve
-
Constructor Details
-
ValuedEnum
Constructor for enum item.- Parameters:
name
- the name of enum itemvalue
- the value of enum item
-
-
Method Details
-
getEnum
Gets an
Enum
object by class and value.This method loops through the list of
Enum
, thus if there are manyEnum
s this will be slow.- Parameters:
enumClass
- the class of theEnum
to getvalue
- the value of theEnum
to get- Returns:
- the enum object, or null if the enum does not exist
- Throws:
IllegalArgumentException
- if the enum class isnull
-
getValue
public final int getValue()Get value of enum item.
- Returns:
- the enum item's value.
-
compareTo
Tests for order.
The default ordering is numeric by value, but this can be overridden by subclasses.
NOTE: From v2.2 the enums must be of the same type. If the parameter is in a different class loader than this instance, reflection is used to compare the values.
- Specified by:
compareTo
in interfaceComparable
- Overrides:
compareTo
in classEnum
- Parameters:
other
- the other object to compare to- Returns:
- -ve if this is less than the other object, +ve if greater than,
0
of equal - Throws:
ClassCastException
- if other is not anEnum
NullPointerException
- if other isnull
- See Also:
-
toString
Human readable description of this
Enum
item.
-