dicates unbounded,
 although still subject to resource constraints of the system.</p></div>
<dl class="notes">
<dt>Returns:</dt>
<dd>upper limit on asynchronous execution.</dd>
</dl>
<dl class="notes">
<dt>Default:</dt>
<dd>-1</dd>
</dl>
</section>
</li>
<li>
<section class="detail" id="virtual()">
<h3>virtual</h3>
<div class="member-signature"><span class="return-type">boolean</span>&nbsp;<span class="element-name">virtual</span></div>
<div class="block"><p>Indicates whether this executor is requested to
 