From the spec for java.awt.GraphicsDevice.setFullScreenWindow(Window w):
"w - a window to use as the full-screen window"

From the Spec for java.awt.GraphicsDevice.getFullScreenWindow():
"Returns the Window object representing the full-screen window if the device is in full-screen mode."

The spec need clarification: does getFullScreenWindow() method always return the same object that has been used in previous setFullScreenWindow() calling or not?

In other words, the following code:

    graphicsDevice.setFullScreenWindow(w);
    return graphicsDevice.getFullScreenWindow();

certainly returns w or not?