title: Check the Number of threads available in ThreadPool at any time
body: <p>Where and how to check through code number of threads available in threadpool. </p>
  
  <p>What i want is:
  For example if no of threads in threadpool are 10 then at any given time I should not be using say more than 3 threads. Once an existing thread gets free, I should start a new task, keeping max count 3.</p>