Uptain system icon/graphics: Black arrow pointing down

A lot of applications make use of a little "expand" black arrow icon in toolbars and frames (Firefox, Thunderbird, OO to name a few). I can find the right pointing arrow (the one used in expanding menus) but not the one pointing downwards.

How do I uptain this little image from Java? I assume it exists as a resource somewhere, however I have been unable to locate it in the UIManager class. Currently I am providing my own icon, but I would prefer to get it programmatically.

Sincerely,
Casper
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