Java Map compiler error with generic

Question

// I know that this method will generated duplicate 
// trim keys for the same value but I am just
// trying to understand why we have a compile error:
// The method         


        

Answer 1

You can use type inference in a helper method, if you want to keep the clean method signature (the client of trimKeyMap shouldn't have to use a generic method):

void trimKeyMap(final Map map) {
    for (final String key : map.keySet()) {
        trim(map, key);
    }
}

private  void trim(final Map map, final String key) {
    map.put(StringUtils.trim(key), map.get(key));
}

This is called wildcard capture and is discussed more here: http://www.ibm.com/developerworks/library/j-jtp04298/