title: String replace function
body: <p>I have following string</p>
  
  <pre><code>String str = "replace :) :) with some other string";
  </code></pre>
  
  <p>And I want to replace first occurance of <code>:)</code> with some other string</p>
  
  <p>And I used <code>str.replaceFirst(":)","hi");</code></p>
  
  <p>it gives following exception</p>
  
  <blockquote>
    <p>"Unmatched closing ')'"</p>
  </blockquote>
  
  <p>I tried using <code>replace</code> function but it replaced all occurance of <code>:)</code>.</p>