src/main/java/seedu/address/logic/parser/ParserUtil.java
public static Optional<TrackingNumber> parseTrackingNumber(Optional<String> trackingNumber)
            throws IllegalValueException {
        requireNonNull(trackingNumber);
        return trackingNumber.isPresent() ? Optional.of(new TrackingNumber(trackingNumber.get())) : Optional.empty();
    }
/**
     * Parses a {@code Optional<String> trackingNumber} into an {@code Optional<TrackingNumber>} if
     * {@code trackingNumber} is present.
     * See header comment of this class regarding the use of {@code Optional} parameters.
     */
Parses a  Optional trackingNumber into an  Optional if
trackingNumber is present.
See header comment of this class regarding the use of  Optional parameters.
Parses a Optional trackingNumber into an Optional if trackingNumber is present . See header comment of this class regarding the use of Optional parameters .
public static Optional<TrackingNumber> parseTrackingNumber(Optional<String> trackingNumber)
            throws IllegalValueException {
        requireNonNull(trackingNumber);
        return trackingNumber.isPresent() ? Optional.of(new TrackingNumber(trackingNumber.get())) : Optional.empty();
    }
public static Optional < TrackingNumber > parseTrackingNumber ( Optional < String > trackingNumber ) throws IllegalValueException { requireNonNull ( trackingNumber ) ; return trackingNumber . isPresent ( ) ? Optional . of ( new TrackingNumber ( trackingNumber . get ( ) ) ) : Optional . empty ( ) ; }
Parses a {@code Optional<String> trackingNumber} into an {@code Optional<TrackingNumber>} if
 {@code trackingNumber} is present.
Parses a { @code Optional<String > trackingNumber } into an { @code Optional<TrackingNumber > } if { @code trackingNumber } is present .