When using com.sun.awt.AWTUtilities, Eclipse gives a error:

- Access restriction: The method setWindowOpacity(Window, float) from the type AWTUtilities is not accessible due to restriction on requiredlibrary C:\Program Files\Java\jre6\lib\rt.jar
- Access restriction: The type AWTUtilities is not accessible due to restriction on required library C:\Program Files\Java\jre6\lib\rt.jar

You can fix it like this:

Preferences -> Java -> Compiler -> Errors/Warnings -> Deprecated and restricted API ->

Forbidden reference -> change "error" to "warning"