code: public void truncate(final long len) throws SQLException {
          synchronized (this) {
              if (this.underlying == null) {
                  if (len < 0) {
                      throw new SQLException("Invalid length: " + len);
                  } // end of if
  
                  return;
              } // end of if
  
              // ---
  
              this.underlying.truncate(len);
          } // end of truncate
      }
docs: {@inheritDoc}