You are, of course, quite right, which is why I said that a Map<String, Object> isn't a Map<Object, Object>. However in Java's typing scheme it is a Map<? exte

You are, of course, quite right, which is why I said that a Map<String, Object> isn't a Map<Object, Object>. However in Java's typing scheme it is a Map<? extends Object, Object>, which represents a key that extends Object (very specific, that) and among other things won't let you insert anything into it.