title: Remove duplicates from a Java List
body: <p>I want to remove duplicates from a list like bellow</p>
  
  <pre><code>List&lt;DataRecord&gt; transactionList =new ArrayList&lt;DataRecord&gt;();
  </code></pre>
  
  <p>where the DataRecord is a class</p>
  
  <pre><code>public class DataRecord {
      [.....]
      private String TUN; 
  </code></pre>
  
  <p>and the TUN should be unique </p>