How was rt.jar created for JRE 1.6?
<p>So here is what I did - </p>

<p>I unzipped the contents of rt.jar into a folder called rt. Then, inside rt folder, I executed the following jar command</p>

<pre><code>jar cf rt.jar *
</code></pre>

<p>This should create a jar file with the same classes as that in the original rt.jar file. </p>

<p>However, the file sizes of the two files are significantly different. </p>

<pre><code>Original rt.jar      -&gt; 43.1 MB
Newly created rt.jar -&gt; 20.6 MB
</code></pre>

<p>Note that the size of the unzipped contents for both the jar files is the same. This makes me think that the original rt.jar wasn't created using the jar command. So how was it created?</p>
