What's the use of “enum” in Java? [duplicate]

Answer 1

You use an enum instead of a class if the class should have a fixed enumerable number of instances.

Examples:

• DayOfWeek  = 7 instances → enum
• CardSuit    = 4 instances → enum
• Singleton  = 1 instance   → enum
  
  
• Product      = variable number of instances → class
• User            = variable number of instances → class
• Date            = variable number of instances → class

Answer 2

Java programming language enums are far more powerful than their counterparts in other languages, which are little more than glorified integers. The new enum declaration defines a full-fledged class (dubbed an enum type). In addition to solving all the problems(Not typesafe, No namespace, Brittleness and Printed values are uninformative) that exists with following int Enum pattern which was used prior to java 5.0 :

public static final int SEASON_WINTER = 0;

it also allows you to add arbitrary methods and fields to an enum type, to implement arbitrary interfaces, and more. Enum types provide high-quality implementations of all the Object methods. They are Comparable and Serializable, and the serial form is designed to withstand arbitrary changes in the enum type. You can also use Enum in switch case.

Read the full article on Java Enums http://docs.oracle.com/javase/1.5.0/docs/guide/language/enums.html for more details.