How to produce error for item not being in array list
<p>I'm trying to select an item from an array list by calling its ID number and I need a Dialog error to show up if the ID number is not associated with any item in the array list.</p>

<p>I know how to code a dialog box but I don't know how to make it pop out when the ID number I type in doesn't match anything in the array list.</p>
