Disclaimer: The original post is available in PT-BR https://dev.to/hugaomarques/o-novo-switch-case-no-java-17-e-21-3ffg

The switch case in Java 17 and 21 brought several improvements that make Java programming easier. From compile-time errors to yield, there's a lot of cool stuff to explore! Let's check out the main updates! 🎉

1. Forget the default!

Now the compiler will notify you if you forget a case, making your code safer. If all possible values are covered, you can skip the default. The best part? Compile-time errors ensure no scenario is left out! 🎯

Let's look at an example showing a compile-time error when a value is added to an enum but not covered in the switch case.

enum Shape { CIRCLE, SQUARE }

// Later we add TRIANGLE to the enum
enum Shape { CIRCLE, SQUARE, TRIANGLE }

Shape shape = ...;
switch (shape) {
    case CIRCLE -> System.out.println("It's a circle!");
    case SQUARE -> System.out.println("It's a square!");
}

Here, the compiler will throw an error saying that the value TRIANGLE has not been handled in the switch. This happens because all enum values need to be covered in the switch case—ensuring no scenario is left out and keeping the code more robust and secure! Without the default, you can be sure all cases are handled. ✨

Compile-time error:

Error: The switch statement does not cover all possible values of the enum: TRIANGLE

2. Yield!

Now the switch can return values with yield, making the code cleaner and more expressive. Forget about confusing returns and enjoy the simplicity. The result? Cleaner and more direct code! 🔄

Example with yield

String message = switch (day) {
    case MONDAY -> {
        System.out.println("Starting the week!");
        yield "Back to work!";
    }
    case FRIDAY -> {
        System.out.println("Weekend is coming!");
        yield "Almost there!";
    }
    case SATURDAY, SUNDAY -> "Enjoy the weekend!";
};

Here, yield allows us to return values directly within the switch without complications. 🚀

3. Support for Enums and Sealed Types

Support for enums and sealed types in switch case has been improved! Now, enums are handled more fluidly, and with sealed types, we can ensure all subtypes are covered in the switch, making the code more predictable and secure. 🚀

Example with Sealed Types

sealed interface Shape permits Circle, Square {
    // Can add common methods or properties
}

final class Circle implements Shape {
    // Implementation of Circle class
}

final class Square implements Shape {
    // Implementation of Square class
}

Shape shape = ...;
switch (shape) {
    case Circle c -> System.out.println("It's a circle with radius: " + c.getRadius());
    case Square s -> System.out.println("It's a square with side: " + s.getSide());
}

In this example, Shape is a sealed interface, and we ensure that all possible subclasses of Shape (in this case, Circle and Square) are covered in the switch case. The compiler helps ensure that no case is missed, increasing the security of the code. 🔒

4. Type Deconstruction with Pattern Matching

And it doesn't stop there! We also have type deconstruction in the switch case, which allows us to perform pattern matching directly on objects. This makes the code more powerful and flexible.

Example with Pattern Matching

switch (obj) {
    case Point(int x, int y) -> System.out.println("Point with coordinates: (" + x + ", " + y + ")");
    case Circle c -> System.out.println("Circle with radius: " + c.getRadius());
}

The power of pattern matching gives us greater control over types! 🔥

Stay Tuned! 🚨

Coming soon, we'll discuss Sealed Types and how, along with the new switch, they open a new paradigm in Java programming 👀. So stay tuned for next posts!