code: public long getLastModified( DirectoryEntry directoryEntry )
          throws IOException
      {
          long lastModified = 0;
          Entry[] entries = listEntries( directoryEntry );
          if ( entries != null )
          {
              for ( Entry entry : entries )
              {
                  lastModified = Math.max( lastModified, entry.getLastModified() );
              }
          }
          return lastModified;
      }
docs: {@inheritDoc}