From TeamDev Ltd.:
JxCapture is a Java library that allows adding different screen capturing abilities to your Java software. This cross-platform library provides a full-featured screen capture API, allowing you to capture any graphic element on the screen and then manipulate it as a java, awt, image, and BufferedImage object in your Java code. Multiple screen capture operations include full-screen capture (available on multiple monitors), active window capture, object capture of any UI element like window, button, and menu, and rectangular region capture. Extensive capture options like capture transparent windows, mouse cursor inclusion, and easy-to-set keyboard shortcuts.