IllegalStateException
class IllegalStateException extends RuntimeException
The call arrived at the wrong moment: the arguments may be perfectly valid, but the object is not in a state that allows it.
Thrown by requireState.
Every class in this hierarchy takes an optional message, another exception whose message it reuses, or nothing at all. isException recognises all of them; a plain Error is not one.
Examples
Throwing and catching
throw new IllegalStateException("something specific about this call");
try {
doWork();
} catch (error) {
if (error instanceof IllegalStateException) {
// handled
}
}
See also
Source
23 September 2026
This documentation was generated with AI (Claude) from the library's source code.