title: Would an inner static runnable in a singleton block if used as wrapper for callables, if it modifies a singleton's static param?
body: <p>1) Is there a chance that an inner static <code>Runnable</code> class can block if it modifies a static <code>ConcurrentHashMap</code> in the outer singleton, after it calls a <code>Callable</code>?  I'm thinking about a scenario where the modification is made to the same item in the map by multiple runnables at the same time.  Multiple runnables are ran in a static <code>ThreadPoolExecutor</code> in the outer singleton.</p>
  
  <p>2) Would the callable be called in the same <code>Thread</code> as the runnable, if i do a <code>val = myCallable.call()</code>?    It modifies the concurrenthashmap depending on the result of a callable.</p>