why it's so different between "long var = System.nanoTime()" and "System.nanoTime()" on time used?
<p>I make a benchmark like this :</p>

<pre><code>for (int i = 0; i &lt; 1000 * 1000; ++i) {
    long var = System.nanoTime();
}
</code></pre>

<p>it takes 41 ms in my computer with jdk6.0</p>

<p>the follow code only costs 1 ms!!!</p>

<pre><code>for (int i = 0; i &lt; 1000 * 1000; ++i) {
    System.nanoTime();
}
</code></pre>

<p>I think may be that time is costed by long var , so I make a test like this :</p>

<pre><code> for (int i = 0; i &lt; 1000 * 1000; ++i) {
    long var = i;
}
</code></pre>

<p>it only costs 1 ms!!!</p>

<p>So,Why the first code block is so slow?
I'm a Chinese. Sorry for my poor English!</p>
