thread safe for instance fields

Question

when programming for a thread safe project, how to determine which field should be thread safe. for example we have a class in a project called TestThreadSafe in a multithread project.

public class TestThreadSafe  {
    public AtomicLong pCounter = new AtomicLong();
    public AtomicLong mCounter = new AtomicLong();
    protected final ConcurrentMap<K, V> Map = new ConcurrentHashMap<K, V>();
    private ScheduledExecutorService ses;
    private String dir;
}

Here, why do not define ses and dir as final or volatile fields?

Answer 1

Key notes:

1. If your variables are not modified by multiple threads, don't use anything
2. If your variable reference does not change after creation, use final
3. If your variable is modified by single thread and accessed by other threads, use volatile
4. If your variables are modified and accessed by multiple threads: a. Use AtomicXXX if your operations are Atomic - single step transaction b. Use synchronized or Lock API if you have a code block to be guarded

You can find more details about high level concurrency constructs here

Related SE questions:

What is the difference between atomic / volatile / synchronized?

What is meant by "thread-safe" code?