Jothi, Hashtable and Vector has the methods which are syncronized and are thread safe. Syncronized collections can be made through the utility methods in Collections class from the existing collection.
there are methods in java.util.Collections that return a thread safe collection from a non thread safe one. All these methods names start with "synchronized". e.g. List<Double> list = new ArrayList<Double>(); List<Double> safe; safe = Collections.synchronizedList(list);