title: How to achieve fixed thread pool without using ExecutorService
body: <p>I have code block like this </p>
  
  <pre><code>   static ExecutorService executor = Executors.newFixedThreadPool(4);
     Runnable worker = new CsvToJavaObject(newFilePath);
     executor.execute(worker);
  </code></pre>
  
  <p>I want to limit the number of threads to n(4) and not use Executor Service.How can i do it ? </p>