public double errorValue(boolean calculate){
  if (!Double.isNaN(m_unitValue) && Double.isNaN(m_unitError) && calculate) {
    m_unitError=m_methods.errorValue(this);
  }
  return m_unitError;
}

public double errorValue ( boolean calculate ) { if ( ! Double . isNaN ( m_unitValue ) && Double . isNaN ( m_unitError ) && calculate ) { m_unitError = m_methods . errorValue ( this ) ; } return m_unitError ; }
call this to get the error value of this unit .
