Performing math operation when operator is stored in a string
<p>I have 2 integers:</p>

<pre><code>int first= 10;
int second = 20;
</code></pre>

<p>and a string representing the operation (one of <code>+</code>, <code>-</code>, <code>/</code>, or <code>*</code>):</p>

<pre><code>String op = "+";
</code></pre>

<p>How can I get the result of 10 + 20 in this example?</p>
