Switch Expressions

Introduced in Java 14, Switch Expressions upgrade the legacy switch statement, introducing expression-based returns, arrow labels, and strict compile-time exhaustiveness checking.

Arrow Labels vs. Yield

• Arrow Syntax (->): Eliminates fall-through behavior. Only the matching block executes, no break required.
• yield Keyword: Used to return a value from a multi-line block inside a switch expression.
• Exhaustiveness: The compiler forces the switch to cover all possible input values. For enums, all constants must be handled. For other types, a default block is required.

Code Walkthrough

This program demonstrates a switch expression returning values using arrow syntax.

public class SwitchExpressionDemo {
    enum Day { MON, TUE, WED, SAT, SUN }
public static void main(String[] args) {
        Day day = Day.SAT;
// Expression return assignment
        String type = switch (day) {
            case MON, TUE, WED -> "Weekday";
            case SAT, SUN -> {
                System.out.println("Weekend reached!");
                yield "Weekend"; // Multi-line return keyword
            }
        }; // Semicolon required!
System.out.println("Type: " + type);
    }
}

Interview-Relevant Information