title: How to modify core applications
body: <p>I want to modify the core applications like Settings.apk and install on my own android phone.I don't want to publish it on market. I have following doubts</p>
  
  <ol>
  <li>Where can I get source code for core applications?</li>
  <li>What are the things I need  to do this?</li>
  <li>Please tell me steps to do this.</li>
  </ol>