java - do I need a lock? -

myobject myobj ...  public void updateobj(){      myobject newobj = getnewmyobject();      myobj = newobj; }  public int getsomething(){      //o(n^2) operation performed in getsomething method      int = myobj.getsomething();      return something; } 

suppose main thread periodically calls updateobj() , child thread calling getsomething() method pretty often.

do need lock (or declare methods synchronized) before myobj = newobj; , int = myobj.getsomething();

someone argued don't need lock here because in java, assignment operations (e.g myobj = newobj;) atomic. don't myobj.getsomething(); not atomic operation o(n^2) think locking still needed. correct?

thanks in advance.

you need declare myobject volatile, otherwise getsomething() method may not see updated object. other cannot see synchronization issues in above code