Check if a selectable is registered. This can be used for tracking
whether a given selectable has been registerd with an external event
loop.
<p>
<em>Note:</em> the reactor code, currently, does not use this flag.
@return <code>true</code>if the selectable is registered.
Check if a selectable is registered. This can be used for tracking whether a given selectable has been registerd with an external event loop. <p> <em>Note:</em> the reactor code, currently, does not use this flag. @return <code>true</code>if the selectable is registered.