GraphicsEnvironment.getMaximumWindowBounds() does not take into account screen insets - system menu and task bar.
It just return screen size.

JDK: jdk 6 (6u131b06 was tested). (not applicable to 7, 8, 9)
Tests:
AWT_UndecoratedFrame/Automated/AWT/FullSize AWT_UndecoratedFrame/Automated/Swing/FullSize

OS specific: Solaris; (tested on Solaris 11). Works good on Windows
Regression: no (tested on jdk1.6.0_105b15 - also fails)
Steps to reproduce:

Dimension dimensionOfFullScreen = Toolkit.getDefaultToolkit()
                    .getScreenSize();
Dimension dimensionOfMaxWindowBounds = GraphicsEnvironment
                  .getLocalGraphicsEnvironment().getMaximumWindowBounds()
                    .getSize();

dimensionOfMaxWindowBounds should differ from dimensionOfFullScreen if there are menu bar or task bar.