There are 3 methods in 'java.util.TimeZone' class, which have suspicious 'synchronized' modifier on them.
Seems that all of them are leftovers and can be removed.

1.
    public static synchronized TimeZone getTimeZone(String ID) {
        return getTimeZone(ID, true);
    }

This method doesn't modify any fields and just calls another method 'getTimeZone(String, boolean)'. Method 'getTimeZone(String, boolean)' is also called in another non-syncrhonized public TimeZone method - 'getTimeZone(ZoneId)'.

2.
    public static synchronized String[] getAvailableIDs(int rawOffset) {
        return ZoneInfo.getAvailableIDs(rawOffset);
    }

This method just call static method in 'ZoneInfo' class, which calls ZoneInfoFile method, which construct array from data initialized in <clinit>.

3.
    public static synchronized String[] getAvailableIDs() {
        return ZoneInfo.getAvailableIDs();
    }

This method just call static method in 'ZoneInfo' class, which calls ZoneInfoFile method, which construct array from data initialized in <clinit>.