title: remove duplicates from List<String[]>
body: <p>I'm looking for a nice way to remove duplicates from a list.</p>
  
  <pre><code>List&lt;String[]&gt; rowList = new ArrayList();
      rowList.add(new String[]{"1","a", "abc"});
      rowList.add(new String[]{"2","b", "def"});
      rowList.add(new String[]{"3","c", "ghi"});
      rowList.add(new String[]{"4","a", "jkl"});
      rowList.add(new String[]{"5","d", "mno"});
      rowList.add(new String[]{"6","e", "pqr"});
      rowList.add(new String[]{"7","b", "stu"});
  </code></pre>
  
  <p>From this rwoList, i only want entries: 1,2,3,5 and 6. This means i have only one column of intrest, in this case column 2 (a, b, c,..)
  This is only an easy example i have to handle hugh amount of tables which have 300 columns and min 300000 rows. Another important point is, that i don't won't loose the orientation within the list.</p>
  
  <p>Note: I receive the data from a csv file.</p>