Method::getMethod()'s 2nd parameter is variadic. So you don’t need to instantiate an array for it:
callbackClass.getMethod(callbackMethod, String.class, int.class);
And no need to 3 catch () blocks. This 1 deals w/ all of them:
} catch (final ReflectiveOperationException e) {
Docs.Oracle.com/en/java/javase/11/docs/api/java.base/java/lang/ReflectiveOperationException.html