public void add(String key,Serializable value){
  List<Serializable> entries=data.get(key);
  if (entries == null) {
    entries=new ArrayList<Serializable>();
    data.put(key,entries);
  }
  entries.add(value);
}

public void add ( String key , Serializable value ) { List < Serializable > entries = data . get ( key ) ; if ( entries == null ) { entries = new ArrayList < Serializable > ( ) ; data . put ( key , entries ) ; } entries . add ( value ) ; }
adds the data to the sequence of observations with the specified key .
