I covered all subclasses of a sealed class in a switch expression, but the Java compiler still claims the switch is not exhaustive. Why?

Question

Assume the structure:

sealed class Shape permits Circle, Quadrangle {}

sealed class Quadrangle extends Shape permits Diamond, Rectangle { }
final class Rectangle extends Quadrangle {}
final class Diamond extends Quadrangle {}
final class Circle extends Shape {}

Then when I have e.g. such switch statement:

switch (shape) {
    case Rectangle _-> System.out.println("");
    case Diamond _-> System.out.println("");
    case Circle _-> System.out.println("");
}

I have information about not covering all cases and forced to implement default. In my opinion this is some bug or something. It should not be that way. As I cover all cases. Is there a way to achieve the exhaustiveness of the switch statement and if yes then how?

Mark Rotteveel · Accepted Answer · 2026-04-04 10:20:37Z

In Java, a sealed class is not implicitly abstract¹. Which means your hierarchy allows Shape and Quadrangle instances that are not one of Rectangle, Diamond, or Circle. Thus, your switch is not exhaustive.

There are at least three solutions. I suspect the first one would fit your scenario best and is the one you're looking for.

Make Shape and Quadrangle abstract (whether abstract class or interface)

abstract sealed class Shape permits Quadrangle, Circle {}
abstract sealed class Quadrangle permits Rectangle, Diamond {}

Add cases for Shape and Quadrangle to the switch

switch (shape) {
  case Rectangle _ -> {}
  case Diamond _ -> {}
  case Circle _ -> {}
  // Must put least specific types last
  case Quadrangle _ -> {}
  case Shape _ -> {}
}

Add a default case to the switch

switch (shape) {
  case Rectangle _ -> {}
  case Diamond _ -> {}
  case Circle _ -> {}
  default -> {}
}

^{1. In other languages, such as Kotlin, a sealed class is implicitly abstract. This may be the source of your confusion.}

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