Enum In Java

August 1, 2023

enums in java

What is Enum in Java ?

In a programming language, enumerations are used to represent a set of named constants.Java has a data type called Enum that has a predetermined set of constants.All constants should be written in capital letters in accordance with Java’s naming guidelines. So, we have enum constants in capital letters.It can be used for seasons, directions, days of the week, etc.

Points to remember for Java Enum

  • Enum increases type security
  • Using enum in switches is simple.
  • It is possible to navigate through Enum.
  • Fields, constructors, and methods can be found in enum.
  • Enum can implement numerous interfaces, but it can only internally extend the Enum class.

Enumeration declaration in Java:

Enum declarations can be made inside or outside of classes, but not within methods.
 

Polymorphism in Java

Encapsulation in Java

Abstraction in Java

Multithreading in Java

Syntax :

Run 
// (Note enum keyword instead of
// class keyword)

enum Seaon {
	SPRING,
	SUMMER,
	WINTER;
}

public class Main{
	// Driver method
	public static void main(String[] args)
	{
		Seaon s1 = Seaon.SPRING;
		System.out.println(s1);
	}
}

Output :

SPRING

Explanation :

In this code  we have  defined an enumerated type Season with three values: SPRING, SUMMER, and WINTER.

In the main method, an instance of Season is created with the value SPRING, which is assigned to the variable s1. The println statement then prints the value of s1, which will be SPRING.

java desk gif

Syntax :

Run 
enum Season {
    SPRING, SUMMER, FALL, WINTER
}

public class Main {
    public static void main(String[] args) {
        Season currentSeason = Season.SPRING;
        System.out.println("Current season: " + currentSeason);

        switch (currentSeason) {
            case SPRING:
                System.out.println("Flowers are blooming.");
                break;
            case SUMMER:
                System.out.println("It's hot outside.");
                break;
            case FALL:
                System.out.println("Leaves are changing colors.");
                break;
            case WINTER:
                System.out.println("It's cold outside.");
                break;
        }
    }
}

Output :

Current season: SPRING
Flowers are blooming.

Explanation :

In this example, the enumerated type Season is used to represent the four seasons of the year. In the main method, a variable currentSeason is declared and initialized to Season.SPRING. The println statement then prints the value of currentSeason, which will be SPRING.

The switch statement then uses the currentSeason variable to determine which case to execute. In this case, since currentSeason is equal to Season.SPRING, the message “Flowers are blooming.” will be printed.

Why java Enums ?
To replace the use of int constants in Java, enum was introduced.
Suppose we have used a collection of int constants.

Syntax :

class Size {
   public final static int SMALL = 1;
   public final static int MEDIUM = 2;
   public final static int LARGE = 3;
   public final static int EXTRALARGE = 4;
}

If we print the constants in this case, a problem results. This is due to the fact that only the number, which may not be useful, is printed.So, we can just use enums in place of int constants. For example,

Syntax :

enum Size {
   SMALL, MEDIUM, LARGE, EXTRALARGE
}

Java Enum Class Methods :

Enum classes offer some predefined methods that are immediately usable.
  1. Java Enum ordinal()
  2. Enum compareTo()
  3. Enum toString()
  4. Enum name()
  5. Java Enum valueOf()
  6. Enum values()
1. Java Enum ordinal() :
The position of an enum constant is returned by the method ordinal().

Syntax :

ordinal(SMALL) 
// returns 0
2. Enum compareTo() :
The ordinal value of the enum constants is used by the compareTo() method to compare them. For example

Syntax :

Size.SMALL.compareTo(Size.MEDIUM)
 // returns ordinal(SMALL) - ordinal(MEDIUM)
3. Enum toString() :
The string representation of the enum constants is provided by the toString() method. For example

Syntax :

ordinal(SMALL) 
// returns 0
4.Enum name() :
The defined name of an enum constant is returned as a string by the name() method. The returned value from the name() method is final. For example

Syntax :

name(SMALL)
// returns "SMALL"
5. Java Enum valueOf() :
When a string is provided, the valueOf() method returns an enum constant with the same string name.

Syntax :

Size.valueOf("SMALL")
// returns constant SMALL.
6. Java values() :
The array of enum type that the values() method returns contains all of the enum constants.

Syntax :

Size[] enumArray = Size.value();

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