Advertisement
Google Ad Slot: content-top
Java Enum
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:
- Defined Using
enumKeyword:
- An enum is a distinct data type and is declared using the
enumkeyword.
- Implicit Features:
- Enums are implicitly static and final.
- Enum constants are implicitly public, static, and final.
- Enum in a Class:
- Enums can be declared inside or outside a class but not inside a method.
- Enum With Methods:
- Enums can include fields, constructors, and methods.
- 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);
}
}
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);
}
}
}
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());
}
}
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;
}
}
}
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));
System.out.println("Multiplication: " + Operation.MULTIPLY.apply(x, y));
System.out.println("Division: " + Operation.DIVIDE.apply(x, y));
}
}