What are switch expressions in Java and how do they differ from switch statements?

Switch expressions (JEP 361, finalised in Java 14) make switch a value-producing expression rather than only a control-flow statement. They use the arrow (->) syntax and require exhaustiveness.

// Switch STATEMENT (old style) — fall-through risk
int numLetters;
switch (day) {
    case MONDAY: case FRIDAY: case SUNDAY:
        numLetters = 6; break;
    case TUESDAY:
        numLetters = 7; break;
    default:
        numLetters = 8; break;
}

// Switch EXPRESSION (Java 14+) — exhaustive, no fall-through
int numLetters = switch (day) {
    case MONDAY, FRIDAY, SUNDAY -> 6;
    case TUESDAY               -> 7;
    case THURSDAY, SATURDAY    -> 8;
    case WEDNESDAY             -> 9;
}; // no default — DayOfWeek is exhaustive

// Multi-line arm with yield
int result = switch (x) {
    case 1 -> 10;
    case 2 -> {
        int y = x * x;
        System.out.println("Computing...");
        yield y + 5; // yield produces the value from a block arm
    }
    default -> 0;
};