Is reference update thread safe?

Question

public class Test{
   private MyObj myobj = new MyObj(); //it is not volatile


   public class Updater extends Thred{
      myobje = getNewObjFromDb() ; //not am settin         


        

Answer 1

No, it isn't.

Without volatile, calling getData() from a different thread may return a stale cached value.
volatile forces assignments from one thread to be visible on all other threads immediately.

Note that if the object itself is not immutable, you are likely to have other problems.