Enum

An enum is a special "class" that represents a group of constants (unchangeable variables, like final variables).

To create an enum, use the enum keyword (instead of class or interface), and separate the constants with a comma. Note that they should be in uppercase letters:

Example

enum Level {
  LOW,
  MEDIUM,
  HIGH
}

Enum: short form for enumeration:  a group of named constant

• An enum is a special data type which is basically a collection (set) of constants
• Variables of that type must be equal to one of the constant values that have been predefined. 
• An enum is a special class that defines a set of constants
• To create enum, use the enum keyword (instead of class or interface), separate the constants with comma. 
• Constant should be uppercase letters. 
• While defining enums, the constant should be declared first, prior to any filed or methods
• Semi Colon (;) is optional, however, when there are fields and methods declared inside enum, the list of enum constant must end with semicolon(;)
• enum concept introduced in 1.5 version

public enum Directions{

EAST, WEST, SOUTH, NORTH

}

Here, we have a variable Directions of enum type (class type variable), which is a collection of four constants EAST, WEST, SOUTH, and NORTH

Objective: If we want to represent a group of named constant then we should go for enum. The main objective of enum is to define our own data type(enumerated data type)

Internal implementation of enum: 

• Every enum is internally implemented by using class concept
• Every enum constant is always public, static, and final
• Every enum constant represent an object of the type enum
• Every enum constant is static and hence we can access by using enum name.
• Inside enum, toString method is implemented to return name of the constant directly

package com.enumconcept;

public enum Currency {

PENNY(1), NICKLE(5), DIME(10), QUARTER(25);

private int value;

private Currency(int value) {

this.value = value;

}

public int getValue() {

return value;

}

}

package com.enumconcept;

public class EnumerationExample {

public static void main(String[] args) {

System.out.println("The value of dime is: " + Currency.DIME.getValue());

}

}

Output:

The value of dime is: 10

package com.cerotid.enumconcept;

public enum Weather {

    //CHECKING, SAVING, BUSINESS_CHECKING;

    //choose the account from there

    //whenever you do the account setup

    //Account.Accounttype = Accountype.business_checking

SUMMER ("summer"), WINTER ("winter"), FALL ("fall"), SPRING ("spring");

    

private String weather;

Weather(String weather){

    this.weather = weather;

}

public String getWeather() {

    return weather;

}

public void setWeather(String weather) {

    this.weather = weather;

}

}

package com.cerotid.enumconcept;

public class WeatherTest {

public static void main(String[] args) {

    //System.out.println(Weather.FALL);

    

    Weather weather = Weather.FALL;

    switch (weather) {

    

    case SUMMER:

        System.out.println("Go to vacation");

        break;

        

    case WINTER:

        System.out.println("Go to Infront of fire place");

        break;

        

    case FALL:

    System.out.println("Go to enjoy fall color");

    break;

    

    case SPRING:

        System.out.println("Go to enjoy party");

        break;

        

        default:

            break;

        

    }

    System.out.println(Weather.valueOf("SUMMER"));

}

}

output:

Go to enjoy fall color

SUMMER

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Reference:

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