com.sun.awt.AWTUtilities, Eclipse gives a error

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 required library C:Program FilesJavajre6librt.jar

- Access restriction: The type AWTUtilities is not accessible due to restriction on required library C:Program FilesJavajre6librt.jar

You can fix it like this:

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

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

Don't worry. It works。