title: Remove elements from ArrayList
body: <p>I have to remove elements from <code>ArrayList</code>, but I have not gone through it. Elements which I have to remove are also available in <code>ArrayList</code>. In short, I have to remove one Array List from another Array List. e.g. Suppose </p>
  
  <pre><code>ArrayList&lt;String&gt; arr1= new ArrayList&lt;String&gt;();
  ArrayList&lt;String&gt; arr2 = new ArrayList&lt;String&gt;();
  arr1.add("1"); 
  arr1.add("2"); 
  arr1.add("3"); 
  
  arr2.add("2"); 
  arr2.add("4"); 
  </code></pre>
  
  <p>Now, I have to remove elements which are in arr2 from arr1. So, that I have final answer as 1 and 3.
  What needs to be done?</p>