public String checkParamsNonNegative(){
  String ret="";
  if (param1 < 0) {
    ret=ret.concat(pdf.getParam1Name() + " is negative. \n");
  }
  if (param2 < 0) {
    ret=ret.concat(pdf.getParam2Name() + " is negative. \n");
  }
  if (upperBound < 0) {
    ret=ret.concat("Upper boundary is negative. \n");
  }
  if (lowerBound < 0) {
    ret=ret.concat("Lower boundary is negative. \n");
  }
  return ret;
}

public String checkParamsNonNegative ( ) { String ret = "" ; if ( param1 < 0 ) { ret = ret . concat ( pdf . getParam1Name ( ) + " is negative. \n" ) ; } if ( param2 < 0 ) { ret = ret . concat ( pdf . getParam2Name ( ) + " is negative. \n" ) ; } if ( upperBound < 0 ) { ret = ret . concat ( "Upper boundary is negative. \n" ) ; } if ( lowerBound < 0 ) { ret = ret . concat ( "Lower boundary is negative. \n" ) ; } return ret ; }
checks to make sure that there are no negative parameters .
