title: find out the elements of an arraylist which is not present in another arraylist
body: <p>I have to find a best way to find out that elements which is not presented in the second arraylist. 
  suppose </p>
  
  <pre><code>Arraylist a,b, 
  
  Arraylist a={1,2,3,4,5};
  Arraylist b={2,3,4};
  </code></pre>
  
  <p>So basically what I want is to find out that elements of <strong>a</strong> which is not present in <strong>arraylist b</strong>.</p>
  
  <p>So what is the best solutions to do that?</p>