HashMap<V, Collection<K>> maybe. Generally, different keys can be mapped on the same value. So one value corresponds to a set of keys.

I mean that in countLiveNeighbors, if (isLiving){result++;} can be replaced with result+=isLiving, which is faster.

When you suggest to make this.message volatile, you mean to make sure assigment to message happens before reading it. But as docs.oracle.com/javase/7/docs/api/java/util/concurrent/… reads, Actions in a thread prior to submitting a Runnable object to an Executor happen-before its execution begins, perhaps in another thread, so no need to make it volatile or put another synchronized block.

do google search for "recursive descent parser for arithmetic expressions".

What is the sense of doing so?

For learning purposes, read more code written by qualified programmers. Sources of main java libraries, including ArrayBlockingQueue, are available. But very often that code is overoptimized, so reader can get habits of bad style. For beginners, style is more important than execution speed.

HashSets are never ordered, even if parameter lists in their constructors are.

realFields should be of type Field[], not Set<String>.

Then what? Another method is also suboptimal, though in a different way.