Reproduced with DISPLAY set to: Solaris, GNome, taskbar at the top of the screen

Method of class java.awt.GraphicsDevice

public void setFullScreenWindow(Window w)

says

    "Simulated full-screen mode resizes the window to the size of the screen and positions it at (0,0)"

This is not always true. Actually the window's left top corner is not moved to (0,0) if a "taskbar" in GNome environment is located at the top side of the screen, so Y position of window will not be zero. (However the size of a frame is perfectly equal to the screen size)

The following JCK testcase will due to this issue
api/java_awt/GraphicsDevice/indexTGF.html#SetFullScreenWindowSimulated[resizing]

----------out1:(9/742)----------
Testcase "position" failed with message: Window Y coordinate is expected to be 0.0
Expected equal to : "0.0", was given: "27.0"
at com.sun.tck.lib.Assert.assertEquals(Assert.java:142)
at com.sun.tck.lib.Assert.assertEquals(Assert.java:133)
at javasoft.sqe.tests.api.java.awt.GraphicsDevice.SetFullScreenWindowSimulated.position(SetFullScreenWindowSimulated.java:72)
Testcase "position" failed with arguments [java.awt.Frame[frame0,0,27,8x25,layout=java.awt.BorderLayout,title=,resizable,normal], X11GraphicsDevice[screen=0]]
position: Failed. test cases: 2; passed: 1; failed: 1; first test case failure: position
size: Passed. test cases: 2; all passed
STATUS:Failed.test cases: 2; passed: 1; failed: 1; first test case failure: position
----------out2:(0/0)----------