MissingCasesInEnumSwitch
Switches on enum types should either handle all values, or have a default case.

Category
JDK
Severity
ERROR
Maturity

The problem

Consider a switch statement that doesn’t handle all possible values and doesn’t have a default:

enum Colors { RED, GREEN, BLUE }

switch (color) {
  case RED:
  case GREEN:
    paint(color);
    break;
}

The author’s intent isn’t clear. There are three possibilities:

  1. The default case is known to be impossible. This could be made clear by adding: \ default: throw new AssertionError();

  2. The code intentionally ‘falls out’ of the switch on the default case, and execution continues below. This could be made clear by adding: \ default: // fall out

  3. The code has a bug, and the missing cases should have been handled.

To avoid this ambiguity, the Google Java Style Guide requires each switch statement to include a default statement group, even if it contains no code.

Suppression

Suppress false positives by adding an @SuppressWarnings("MissingCasesInEnumSwitch") annotation to the enclosing element.