No,
you should synchronize on a common lock while accessing the shared static resource.
In this case a valid candidate would be the intrinsic lock of the resource itself i.e
synchronized(resultList) rather than
synchronized(this).
Also, you should synchronize for both reads and writes, which your code currently does not do.
Build a man a fire, and he'll be warm for a day. Set a man on fire, and he'll be warm for the rest of his life.