code: public Collection<ActiveConnectionRecord> get(String identifier) {
          synchronized (records) {
  
              // Get set of active connection records
              Collection<ActiveConnectionRecord> connections = records.get(identifier);
              if (connections != null)
                  return Collections.unmodifiableCollection(connections);
  
              return Collections.<ActiveConnectionRecord>emptyList();
  
          }
      }
docs: Returns a collection of active connection records associated with the
  object having the given identifier. The collection will be sorted in
  insertion order. If there are no such connections, an empty collection is
  returned.
  
  @param identifier
  The identifier of the object to check.
  
  @return
  An immutable collection of records associated with the object having
  the given identifier, or an empty collection if there are no such
  records.