public final double errorEstimate(){
  calculate();
  QL.require(!Double.isNaN(this.errorEstimate),"error estimate not provided");
  return errorEstimate;
}

public final double errorEstimate ( ) { calculate ( ) ; QL . require ( ! Double . isNaN ( this . errorEstimate ) , "error estimate not provided" ) ; return errorEstimate ; }
returns the error estimate on the npv when available .
