I considered Optional<Class<?>>. I believe it is rare to have a JNI attached thread calling StackWalker::getCallerClass from native. Most common cases will find a caller class. Returning an Optional will force most common uses to handle the case if it’s absent. It’s a tradeoff that I think it’s better to return Thread.class for the JNI attached thread calling getCallerClass in native which would rarely happen.
+1 on returning Thread.class in these cases. Its a pragmatic compromise.
