public boolean isValidExchange(SerialNumber serialNumber, Exchange request) {
// create upper bound for calculation of average
SerialNumber validityCheckBound =
new SerialNumber(serialNumber.getSerialNumber().add(ADD_FOR_BOUND));
// find the set of serial #'s strictly greater than serialNumber and <= validityCheckBound
NavigableSet<SerialNumber> temp =
getExclusiveToInclusiveSubset(
request.getCompatibleProducts(), serialNumber, validityCheckBound);
// find the st of serial #'s strictly greater than serialNumber and less than average
// if empty, no compatible product exists
return !(getExclusiveSubset(request, serialNumber, average(temp)).isEmpty());
}
// returns validity of given serial number
public static Boolean isValidSerialNumber(SerialNumber serialNumber) {
// check whether even and the third bit is set
return serialNumber.isOdd() && checkLowerBound(serialNumber);
}