title: Creating a random 4 digit number, and storing it to a string
body: <p>I'm trying to create a method which generates a 4 digit integer and stores it in a string.
  The 4 digit integer must lie between 1000 and below 10000. Then the value must be stored to <code>PINString</code>.
  Heres what I have so far. I get the error <code>Cannot invoke toString(String) on the primitive type int</code>. How can I fix it?</p>
  
  <pre><code>   public void generatePIN() 
     {
  
          //generate a 4 digit integer 1000 &lt;10000
          int randomPIN = (int)(Math.random()*9000)+1000;
  
          //Store integer in a string
          randomPIN.toString(PINString);
  
      }
  </code></pre>