Written In The Font

When we to set some constants for projects, we always use ‘public static final’to set Int or String constants.Or sometimes,we can also set the paramters in properties.When the project starts,we can get the properties to use them.Today,we can use Enum (JDK 1.5).

Three pieces:
  1. An Example to Know Enum

  2. How to use EnumSet and EnumMap

  3. Enum Analysis

An Example to Know Enum

Firstly,we use the Enum to implements Operation.

Run as Java application,we can see the Console.The result shows operations

Q:‘The enum is just like class?’

A:Yep,I think that Enum is a nice type.So let us know some methods by apis:

1. Firstly,we can make an abstract method ‘apply()’ ,then set in the constant-specific class body. Its called constant-specific method implementation.

2. We can make constructor with fields to make the enum has vales.(Like String or int …)

3. toString() method : Returns the name of this enum constant, as contained in the declaration. This method may be overridden, though it typically isn’t necessary or desirable. An enum type should override this method when a more programmer-friendly string form exists.

4. ‘vales()’ method :to get all enum objects. And ‘getValue()’ can get the enum object’ value.

Note ‘Its easy to learn how to use.Then learn more and study in depth.’ And in real projects,We can use enums to replace Int or String Enum Pattern.And Enum is also a typesafe enum.

How to use EnumSet and EnumMap

Let us see another example to learn some Sets of Enum.So lets see it:

We can see in Console:

Note： EnumSet or EnumMap is easy for we to use.And with them，we can use enums easily.

Enum Analysis

We use ‘javap -c -private xxx’to know the class:

We can see ‘Enum is a class.just is a class.’but no extends.