rspec/rules/S5194/java/rule.adoc

Many existing switch statements are essentially simulations of switch expressions, where each arm either assigns to a common target variable or returns a value. Expressing this as a statement is roundabout, repetitive, and error-prone.


Java 12 added support for switch expressions, which provide more succinct and less error-prone version of switch.


== Noncompliant Code Example

----
void day_of_week(DoW day) {
    int numLetters;
    switch (day) {  // Noncompliant
      case MONDAY:
      case FRIDAY:
      case SUNDAY:
        numLetters = 6;
        break;
      case TUESDAY:
        numLetters = 7;
        break;
      case THURSDAY:
      case SATURDAY:
        numLetters = 8;
        break;
      case WEDNESDAY:
        numLetters = 9;
        break;
      default:
        throw new IllegalStateException("Wat: " + day);
    }
}

int return_switch(int x) {
    switch (x) { // Noncompliant
      case 1:
        return 1;
      case 2:
        return 2;
      default:
        throw new IllegalStateException();
    }
}
----


== Compliant Solution

----
int numLetters = switch (day) {
    case MONDAY, FRIDAY, SUNDAY -> 6;
    case TUESDAY                -> 7;
    case THURSDAY, SATURDAY     -> 8;
    case WEDNESDAY              -> 9;
};
----