enum keyword

In case of enum

1.       All the constant variable are by default “public static final”, no need to declare explicitly.

2.       All the constant variable are by default of same enum type, no need to provide any data type.

3.       All the constant variables are by default named constants, if we access constant variable then we are able to get name of the constant variables not values of the constant variable.

Syntax  :-

[Access_Modifier] enum Name

{

                ---list of constant variables---

}

Ex code :-

enum User_Status

{

        AVAILABLE, BUSY, IDLE;

}

class Test

{

        public static void main(String[] args)

        {

                        System.out.println(User_Status.AVAILABLE);

                        System.out.println(User_Status.BUSY);

                        System.out.println(User_Status.IDLE);

        }

}

On Command prompt :- 

javap User_Status

if we compile the above enum then compiler will translate enum into the final classs like below.

Compiled from "Test.java"

final class User_Status extends java.lang.Enum<User_Status>{

public static final User_Status AVAILABLE;

public static final User_Status BUSY;

public static final User_Status IDLE;

public static User_Status[] values();

public static User_Status valueOf(java.lang.String);

static {};

In java applications, we are able to use enums like classes, where we are able to declare normal variables, methods, constructors,…. As per the requirement.

Ex code :-

enum Apple

{

        A(500),B(300),C(100);

        int price;

        Apple(int price)

        {

                        this.price=price;

        }

        public int getPrice()

        {

                        return price;

        }

}

class Test

{

        public static void main(String[] args)

        {

                        System.out.println("A Grade Apple:"+Apple.A.getPrice());

                        System.out.println("B Grade Apple:"+Apple.B.getPrice());

                        System.out.println("C Grade Apple:"+Apple.C.getPrice());

        }

}

Output:-

A Grade Apple:500

B Grade Apple:300

C Grade Apple:100

If the compile the above enum then compiler will translate the above enum into final class like below

Ex code:-

final class Apple extends java.lang.Enum

{

        public static final Apple A=new Apple(500);

        public static final Apple B=new Apple(300);

        public static final Apple C=new Apple(100);

        int price;

        Apple(int price)

        {

                        this.price=price;

        }

        public int getPrice()

        {

                        return price;

        }

}