Parsing a string to a java LocalTime

I have a method that can take in a time string in one of the following formats:

1. HHmmss - e.g. 073055 = 07:30:55

2. HHmm - e.g. 0730 = 07:30:00

3. HHmm'H - e.g. 0730H = 07:30:30

4. a whitespace or empty string - return null

My current code is as follows:

private final static String timeFormatPattern = "HHmmss";
private final static DateTimeFormatter timeFormatter = DateTimeFormatter.ofPattern(timeFormatPattern);

private static LocalTime getLocalTime(String inputTime)
{
    if (inputTime.trim().equals(""))
    {
        return null;
    }
    else
    {
        char secondsIndicator = inputTime.charAt(4);

        if (secondsIndicator == ('H'))
        {
            // H = 30 seconds
            return LocalTime.parse(inputTime.substring(0, 4) + "30", timeFormatter);
        }
        else if (secondsIndicator == (' '))
        {
            // no H = 00 seconds
            return LocalTime.parse(inputTime.substring(0, 4) + "00", timeFormatter);
        }
        else // specific time provided
        {
            return LocalTime.parse(inputTime,timeFormatter);
        }
    }
}

Profiling shows that this method takes 16,439 milliseconds over 7.6 million invocations; and thus is the method with the highest self time in my program's startup.

I have tried splitting this into two methods (one to format the string, and one that simply contains return LocalTime.parse(formattedTime, timeFormatter);), to see whether it was the LocalTime.parse or my string manipulation that was slow. It turns out that 2/3 of the processing is from LocalTime.parse, and the other 1/3 from the string manipulation. This is with half the inputs being of the 4th type (and so not calling the LocalTime.parse at all); and half being of the 2nd or 3rd type.

Am I missing a more efficient way of getting the LocalTime here?