docs: public synchronized boolean put(Object key, byte[] value, int len, long expirationTime)
                      throws IOException,
                      EOFException,
                      FileManagerException,
                      ClassNotFoundException,
                      HashtableOnDiskException {
          if (key == null)
              return false;
          //if ( value == null ) return false;  // comment this line to allow the value=NULL
  
          mapPut(key, value, len, expirationTime, -1, null, null, 0, !ALIAS_ID);
  
          return true;
      }