title: Executor.execute() hangs definitely
body: <p>Im doing nashorn lately and so went to read about the java.util.concurrent.</p>
  
  <p>Ive an issue where i can run simple executors like :</p>
  
  <pre><code>Executors.newFixedThreadPool();
  new ThreadPoolExecutor();
  </code></pre>
  
  <p>The snippets of code runs, but after the task is over the console process doesnt stop like if it hangs waiting something.</p>
  
  <p>Any reason why this happens ?</p>