JHotCorner is a Java library which gives the user the ability to execute code if the mouse is dragged into one of the four monitor corners. You can choose which corner should be active (multiple corners are allowed). It's also possible to show a quarter circle if the corner is active and the mouse hits the radius. Fade-in and fade-out effects are also present. There are different options which you can set, including the radius of the hot corner, whether an image should be shown, displaying of your own image, etc. If you want to set an image, transparent and animated GIFs and transparent PNGs can be used. To register a class, simply implement JHotCornerInterface.