Enums - Revision history

Suhridk: /* Enum Types */

2011-09-04T06:08:08Z

Enum Types

2011-09-01T10:45:31Z

Enum Constants

2011-09-01T10:33:14Z

Enum Constants

2011-09-01T10:31:22Z

Enum Constants

2011-08-15T10:03:47Z

Enum Types

2011-08-15T09:56:05Z

Enum Constants

2011-08-15T09:21:29Z

Enum Types

2011-06-25T18:57:51Z

2011-06-25T18:52:27Z

2011-06-25T18:44:13Z

@@ Line 69: / Line 69: @@
 * '''Cannot''' be declared within methods. (Similar to static inner classes cannot)
+==== Enum Extensibility ====
 * An enum can also implement interfaces. (But not extend classes)
 * Example on how we can create a Runnable enum and use it in a thread.

@@ Line 118: / Line 118: @@
 * The '''type name can be skipped only for methods defined within the enum'''.
 * The type name must also be skipped when using enums in case constants. (The enum type has to be imported unless it is accessible)
 * Enum constants are by default '''final and static.'''
 * NO modifier is allowed for the enum constant.

@@ Line 117: / Line 117: @@
 * An enum constant has to be qualified with its enum type name ! Except when:
 * The '''type name can be skipped only for methods defined within the enum'''.
-* The type name must also be skipped when using enums in case constants. (The enum type has to be imported explicitly)
+* The type name must also be skipped when using enums in case constants. (The enum type has to be imported unless it is accessible)
 * Enum constants are by default '''final and static.'''
 * NO modifier is allowed for the enum constant.

@@ Line 115: / Line 115: @@
 * The constants '''''must be specified''''' in the beginning, before anything else.
 * The enum constants '''must be qualified with the enumtype name''' when used outside the enum.
 * The '''type name can be skipped only for methods defined within the enum'''.
 * Enum constants are by default '''final and static.'''
 * NO modifier is allowed for the enum constant.

@@ Line 72: / Line 72: @@
 * An enum can also implement interfaces. (But not extend classes)
 * Example on how we can create a Runnable enum and use it in a thread.
 <syntaxhighlight lang="java5">

@@ Line 50: / Line 50: @@
 === Enum Types ===
 * They cannot be declared final. Otherwise we cannot have constant specific class bodies, also they cannot be abstract.
 * They can be defined in their own files - like public classes and can be run as a standalone application.
 * Example :

@@ Line 96: / Line 96: @@
 </syntaxhighlight>
-* Enums can be defined within other classes. When it is nested, the enum type becomes implicitly static.
+* Enums can be defined within other classes '''or within other enums.''' When it is nested, the enum type becomes implicitly static.
 * Because of their static nature, Enums can't be defined within regular inner classes or method local inner classes.
 * They can be defined within top level classes or within static inner classes.

@@ Line 214: / Line 214: @@
 * The equals() implementation is just a reference check since enum instances cannot be created by the end user.
 * Thus, for any enum enum1.equals(enum2) is equivalent to enum1 == enum2.
 * The enum class also has couple of static methods which are implicitly provided for all enums (like the length attribute for any array). They are:
 * values() : returns all the Enum constants in the order in which they have been defined.
 * valueOf(String name) : reutrns the Enum constant with the specified name.
 [[Category:OCPJP]]

← Older revision		Revision as of 18:44, 25 June 2011
Line 96:		Line 96:
	</syntaxhighlight>		</syntaxhighlight>

		+	* Enums can be defined within other classes. When it is nested, the enum type becomes implicitly static.
		+	* Because of their static nature, Enums can't be defined within regular inner classes or method local inner classes.
		+	* They can be defined within top level classes or within static inner classes.
		+
		+	<syntaxhighlight lang="java5">
		+
		+	public class Info {
		+
		+	enum Cities {Delhi, Dakar, Denver};
		+
		+	public static enum Directions {LEFT, RIGHT};
		+
		+	}
		+
		+	</syntaxhighlight>

	=== Enum Constants ===		=== Enum Constants ===