title: Spring Batch how to remove duplicate items in processor where last entry have preference before send to item writer
body: <p>I read a flat file (for example a .csv file with 1 line per User, Ex: UserId,age,rate,marks).
  Below is example</p>
  
  <pre><code>user1,27,good,1111111
  user2,56,fair,222222
  user1,28,good,333333
  </code></pre>
  
  <p>So as per above data Item processor should pass user object at row 2 &amp; row 3 to item writer.
  But how to handle duplicated User item in the item processor (where last entry of duplicate user given precedence or should be pass to itemwriter)</p>