Switch on Enum in Java

In Java, you can use a switch statement with enum types to handle different cases based on the values of the enum. Enums are a special type in Java that represent a fixed set of constants, and they can be used effectively with the switch statement to simplify conditional logic.

Example: Using Switch with Enum

Let’s go through an example where we define an enum for days of the week, and then use a switch statement to print a message based on the current day.

// Define an enum for Days of the Week
enum Day {
    MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY
}

public class SwitchEnumExample {
    public static void main(String[] args) {
        Day today = Day.WEDNESDAY;

        // Switch statement based on the enum value
        switch (today) {
            case MONDAY:
                System.out.println("Start of the week!");
                break;
            case TUESDAY:
                System.out.println("It's Tuesday!");
                break;
            case WEDNESDAY:
                System.out.println("Hump day!");
                break;
            case THURSDAY:
                System.out.println("Almost there!");
                break;
            case FRIDAY:
                System.out.println("It's Friday!");
                break;
            case SATURDAY:
                System.out.println("Weekend is here!");
                break;
            case SUNDAY:
                System.out.println("Relax, it's Sunday.");
                break;
            default:
                System.out.println("Invalid day!");
        }
    }
}

Explanation:

1. Enum Declaration: We define an enum named Day with values for each day of the week.
2. Switch Statement: We use a switch statement to perform different actions based on the value of the Day enum. The today variable is assigned the value Day.WEDNESDAY, and the switch will execute the corresponding case for WEDNESDAY.
3. Output:

   Hump day!
   

Important Notes:

• Enums in Java can be used directly in a switch statement since they are considered final and thus are handled more efficiently.
• The switch statement works seamlessly with enums as it matches the enum’s values.
• Always include the break statement at the end of each case to prevent “fall through” from one case to another. However, for handling logic that falls through naturally (e.g., combining cases), you can omit the break statement.

Advantages of Using Enum in Switch:

1. Type Safety: You can only use the constants defined in the enum, ensuring that the switch statement is type-safe.
2. Readability: Using enums with switch statements improves the readability and maintainability of the code since the enum values are descriptive.
3. Error Prevention: Using enums prevents errors such as using invalid strings or numbers in your switch cases.

This pattern is particularly useful for handling state machines, process steps, or any situation where a set of predefined options is involved.