title: Get random position from String based on condition
body: <p>I have one String variable like this:</p>
  <pre><code>var data = &quot;FFFTTFFFT&quot;
  </code></pre>
  <p>I want to get random position of <em>'T'</em> present inside above String for which I am doing like this.</p>
  <pre><code>for (i in data.indices) {
      if (data [i] == 'T') someList.add(i) 
  }
  </code></pre>
  <p>then</p>
  <pre><code>var randPos = someList.random()
  </code></pre>
  <p>I am able to do it using loop but I want to do it in idiomatic way in
  Kotlin.</p>