Java Doc for ValuedEnum.java in  » Library » Apache-common-lang » org » apache » commons » lang » enums » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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.

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.

Human readable description of this Enum item.

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.

Gets an Enum object by class and value.

This method loops through the list of Enum, thus if there are many Enums this will be slow.

Get value of enum item.

Human readable description of this Enum item.