title: Why is Java's SimpleDateFormat not thread-safe?
body: <p>Please  tell with a code example why is SimpleDateFormat not threadsafe. What is the problem in this class?
  <strong>Is The problem with format function of SimpleDateFormat</strong>? 
  Please give a code which demonstrates this fault in class.</p>
  
  <p>FastDateFormat is threadsafe. Why?
  what is the difference b/w the SimpleDateFormat and FastDateFormat?</p>
  
  <p>Please explain with a code which demonstrates this issue?</p>