title: Random over ThreadLocalRandom
body: <blockquote>
    <p>Instances of java.util.Random are threadsafe. However, the concurrent
    use of the same java.util.Random instance across threads may encounter
    contention and consequent poor performance. Consider instead using
    ThreadLocalRandom in multithreaded designs.</p>
  </blockquote>
  
  <p>What kind of contention and thus poor performance ? Can anybody please, explain me here ? I don't know what algorithm goes inside Random and ThreadLocalRandom that makes them different.</p>