In java 8, Map interface was enhances with many useful methods, which allow to avoid calling a few separate Map methods.
One of such example is in sun.util.calendar.ZoneInfoFile#getZoneInfo0 method:

            String zid = zoneId;
            if (aliases.containsKey(zoneId)) {
                zid = aliases.get(zoneId);
            }

Instead we can just call
           
           aliases.getOrDefault(zoneId, zoneId)