Switch & Records

 

Original switch:

int day = 2;
switch (day) {
        case 1:
        System.out.println("Monday");
        break;
                case 2:
                System.out.println("Tuesday");
        break;
default:
        System.out.println("Invalid day");
}

Limitations:

• Switch could only be used with primitive types (int, char, byte, short) and later with enums.
• Required break to avoid falling through cases unintentionally.

Enums in Switch

enum Day { MONDAY, TUESDAY, WEDNESDAY }
Day day = Day.TUESDAY;
switch (day) {
        case MONDAY:
            System.out.println("Monday");
            break;
        case TUESDAY:
            System.out.println("Tuesday");
            break;
default:
        System.out.println("Invalid day");
}

Switch with Strings

String day = "Tuesday";
switch (day) {
        case "Monday":
            System.out.println("Monday");
            break;
        case "Tuesday":
            System.out.println("Tuesday");
            break;
default:
        System.out.println("Invalid day");
}

Switch Expressions

int day = 2;
String dayName = switch (day) {
    case 1 -> "Monday";
    case 2 -> "Tuesday";
    case 2, 3, 4, 5, 6 -> "Weekday";
    default -> "Invalid day";
};
System.out.println(dayName);

• The switch statement can now be used as an expression that returns a value.
• Arrow (->) syntax introduced for cleaner case expressions.
• The break statement is no longer needed in this context.
• Multiple case labels (case 1, 7 ->) can be grouped together to handle cases more concisely.

Pattern Matching

Object obj = 123;
    String result = switch (obj) {
        case Integer i -> "Integer: " + i;
        case String s -> "String: " + s;
        default -> "Unknown type";
    };
System.out.println(result);

• Switch can now match based on the type of the object being switched.
• Automatic casting based on the type pattern (e.g., Integer i).

Expanded Pattern

Shape shape1 = new Circle(5);
Shape shape2 = new Rectangle(4, 6);
Shape shape3 = new Triangle(3, 4);
static double calculateArea(Shape shape) {
    return switch (shape) {
        case Circle c -> Math.PI * c.radius() * c.radius(); // Calculate area for Circle
        case Rectangle r -> r.width() * r.height(); // Calculate area for Rectangle
        case Triangle t when t.base() > 0 && t.height() > 0 -> 0.5 * t.base() * t.height(); // Calculate area for Triangle with guard condition
        default -> throw new IllegalArgumentException("Unknown shape: " + shape);
    };
}

• You can de-structure records in the switch expression, making it easier to work with data classes.
• You can add additional conditions to your case statements, allowing for more granular control over the flow of logic.
• Simplified handling of complex data types like sealed types and records.