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Java Enum

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In Java, an enum is a special data type that represents a group of constants (unchangeable variables). Enums are used when you have a fixed set of predefined values, such as directions (NORTH, SOUTH, EAST, WEST), days of the week, or months.

Key Points About Enums in Java:

  1. Defined Using enum Keyword:
  • An enum is a distinct data type and is declared using the enum keyword.
  1. Implicit Features:
  • Enums are implicitly static and final.
  • Enum constants are implicitly public, static, and final.
  1. Enum in a Class:
  • Enums can be declared inside or outside a class but not inside a method.
  1. Enum With Methods:
  • Enums can include fields, constructors, and methods.
  1. Enum Cannot Extend Classes:
  • Since enums implicitly extend java.lang.Enum, they cannot extend any other class.


Syntax:

enum EnumName {
    CONSTANT1, CONSTANT2, CONSTANT3;
}

Example 1: Basic Enum

enum Direction {
NORTH, SOUTH, EAST, WEST;
}

public class Main {
public static void main(String[] args) {
Direction dir = Direction.NORTH;
System.out.println("Direction: " + dir);
}
}

Try it yourself

Example 2: Iterating Through Enums:

You can use the values() method to iterate over all the constants of an enum.

enum Day {
MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY;
}

public class Main {
public static void main(String[] args) {
for (Day day : Day.values()) {
System.out.println(day);
}
}
}

Try it yourself

Example 3: Enum With Fields and Methods:

Enums can have fields, constructors, and methods. Enum constants can also behave like objects.

enum Level {
LOW(1),
MEDIUM(2),
HIGH(3);

private int value;

// Constructor
Level(int value) {
this.value = value;
}

public int getValue() {
return value;
}
}

public class Main {
public static void main(String[] args) {
Level myLevel = Level.HIGH;

// Access enum constant and its method
System.out.println("Level: " + myLevel);
System.out.println("Value: " + myLevel.getValue());
}
}

Try it yourself

Example 4: Enum With Switch Case

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

public class Main {
public static void main(String[] args) {
Season season = Season.SUMMER;

switch (season) {
case SPRING:
System.out.println("Spring is here!");
break;
case SUMMER:
System.out.println("It's summer time!");
break;
case FALL:
System.out.println("Leaves are falling.");
break;
case WINTER:
System.out.println("It's cold outside.");
break;
}
}
}

Try it yourself

Example 5: Enum With Abstract Methods:

Enums can have abstract methods, and each constant must provide an implementation for it.

enum Operation {
ADD {
public int apply(int a, int b) {
return a + b;
}
},
SUBTRACT {
public int apply(int a, int b) {
return a - b;
}
},
MULTIPLY {
public int apply(int a, int b) {
return a * b;
}
},
DIVIDE {
public int apply(int a, int b) {
return a / b;
}
};

public abstract int apply(int a, int b);
}

public class Main {
public static void main(String[] args) {
int x = 10, y = 5;

System.out.println("Addition: " + Operation.ADD.apply(x, y));
System.out.println("Subtraction: " + Operation.SUBTRACT.apply(x, y));

Try it yourself

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