code: @Override
      public boolean isThreadSafe(Tuple<ScriptEngine, String> key, ScriptEvaluator instance) {
          final ScriptEngineFactory factory = key.first.getFactory();
          final Object threadingAbility = factory.getParameter("THREADING");
          return threadingAbility != null && ("THREAD-ISOLATED".equals(threadingAbility) || "STATELESS".equals(threadingAbility));
      }
docs: /* (non-Javadoc)
  @see org.danann.cernunnos.cache.CacheHelper.Factory#isThreadSafe(java.lang.Object, java.lang.Object)