title: When does ExcecutorService fails during execution?
body: <p>According to the document regarding newFixedThreadPool in Executors, I found</p>
  
  <blockquote>
    <p>If any thread terminates due to a failure during execution prior to
    shutdown, a new one will take its place if needed to execute
    subsequent tasks.</p>
  </blockquote>
  
  <p>While I run my code, I detected my fixed sized threadPool with capacity 5 keep generating threads as time goes like <code>pool-1-thread-3212</code> which suppose to be <code>pool-1-thread-5 or less</code></p>
  
  <p>So I wonder when does ExecutorService decide one of its thread fails and launch new one.</p>
  
  <p>Could anyone guide me the reason why this happen?</p>