Difference between synchronization of field reads and volatile

Question

In a nice article with some concurrency tips, an example was optimized to the following lines:

double getBalance() {
    Account acct = verify(name, password         


        

Answer 1

If multiple threads are modifying and accessing the data, synchronized guarantees data consistency among multiple threads .

if single thread is modifying the data and multiple threads try to read the latest value of data, use volatile construct.

But for above code, volatile does not guaranty memory consistency if multiple threds modify balance. AtomicReference with Double type serves your purpose.

Related SE question:

Difference between volatile and synchronized in Java