how can I define static var in android? : <p>I know this code must be so simple. But I couldn't understand it well.</p>

<pre><code>public final static String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE";
</code></pre>

<p>I know <code>public final static String EXTRA_MESSAGE</code> define an static var.</p>

<p>But what is "com.example.myfirstapp.MESSAGE"?</p>

<p>code is <a href="https://developer.android.com/training/basics/firstapp/starting-activity.html?" rel="nofollow noreferrer">here</a>.</p>
