public double valueAtRisk(final double centile){
  QL.require(centile >= 0.9 && centile < 1.0,"percentile out of range [0.9, 1.0)");
  return -Math.min(percentile(1.0 - centile),0.0);
}

public double valueAtRisk ( final double centile ) { QL . require ( centile >= 0.9 && centile < 1.0 , "percentile out of range [0.9, 1.0)" ) ; return - Math . min ( percentile ( 1.0 - centile ) , 0.0 ) ; }
value - at - risk at a given percentile
