title: Android replace with regex
body: <p>I have a string in Android. I would like to wrap all the instances of 4 or more continuous digits with some html. I imagine this will be done with regex, but I have a hard time getting even the most basic regular expressions to work.</p>
  
  <p>Can someone help me with this?</p>
  
  <p>I would like to change:</p>
  
  <pre><code>var input = "My phone is 1234567890 and my office is 7894561230";
  </code></pre>
  
  <p>To</p>
  
  <pre><code>var output = "My phone is &lt;u&gt;1234567890&lt;/u&gt; and my office is &lt;u&gt;7894561230&lt;/u&gt;";
  </code></pre>