TimeZone validation in Java

Question

I have a string, I need to check whether it is a standard time zone identifier or not. I am not sure which method I need to use.

String timeZoneToCheck = \"UTC\"         


        

Answer 1

I would like to propose the next workaround:

public static final String GMT_ID = "GMT";
public static TimeZone getTimeZone(String ID) {
    if (null == ID) {
        return null;
    }

    TimeZone tz = TimeZone.getTimeZone(ID);

    // not nullable value - look at implementation of TimeZone.getTimeZone
    String tzID = tz.getID();

    // check if not fallback result 
    return GMT_ID.equals(tzID) && !tzID.equals(ID) ? null : tz;
}

As result in case of invalid timezone ID or invalid just custom timezone you will receive null. Additionally you can introduce corresponding null value handler (use case dependent) - throw exception & etc.