Enums in Java

    The Enum is a data type which contains a fixed set of constants. The Java enum constants are static and final implicitly.

• Points to remember for Java Enum

• Enum improves type safety
• Enum can be easily used in switch
• Enum can be traversed
• Enum can have fields, constructors and methods
• Enum may implement many interfaces but cannot extend any class because it internally extends Enum class

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public enum TrafficSignal {

RED("Stop", 30),

YELLOW("Prepare to Stop", 5),

GREEN("Go", 45);

private final String action;

private final int durationSeconds;

// Constructor

TrafficSignal(String action, int durationSeconds) {

this.action = action;

this.durationSeconds = durationSeconds;

}

// Method to get the action associated with the traffic signal

public String getAction() {

return action;

}

// Method to get the duration of the signal in seconds

public int getDurationSeconds() {

return durationSeconds;

}

}

public class Main {

public static void main(String[] args) {

// Using enum constants

TrafficSignal redSignal = TrafficSignal.RED;

TrafficSignal greenSignal = TrafficSignal.GREEN;

// Accessing fields and methods

System.out.println("Red signal: " + redSignal.getAction() + " for " +

redSignal.getDurationSeconds() + " seconds");

System.out.println("Green signal: " + greenSignal.getAction() + " for " +

greenSignal.getDurationSeconds() + " seconds");

}

}

Constructor of enum type is private. If you don't declare private compiler internally creates private constructor.

public enum Day {

SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY;

}

public class Main {

public static void main(String[] args) {

// Retrieves the enum constant associated with the specified string

Day day = Day.valueOf("MONDAY");

System.out.println("Day retrieved using valueOf(): " + day);

// Returns an array containing all of the enum constants

Day[] days = Day.values();

System.out.println("All days retrieved using value():");

for (Day d : days) {

System.out.println(d);

}

// Returns the ordinal value of the enum constant

System.out.println("Ordinal value of TUESDAY: " + Day.TUESDAY.ordinal());

}

}