Why do I have incompatible types error when Iterate Map in Java using keySet()?

Question

sI have Class 1 where I have

protected Map<String, Object> parameter = new HashMap<String, Object>(); I have Class 2 that extends Class1 and where I do

List list = this.dao.createSQLQuery(query, this.parameter);

createSQLQuery method for dao looks like this:

public List createSQLQuery(final String query, final Map parameter) {

                    for (final String key : parameter.keySet()) {

                     . . .
} }

Why do I have a error in the for cycle line - “incompatible types: Object cannot be converted to String”?

As I understand my case is not the raw type issue because I declare parameter as Map<String, Object> so parameter.keySet() has to return set of Strings