Access restriction: The type BASE64Decoder is not accessible due to restr[转]

在Eclipse中编写用java代码时用到了BASE64Decoder，import sun.misc.BASE64Decoder;可是Eclipse提示：
Access restriction : The type BASE64Decoder is not accessible due to restriction on required library C:\Program
files\java\jre6\lib\rt.jar
Access restriction : The constructor BASE64Decoder() is not accessible due to restriction on required library C:\Program files\java\jre6\lib\rt.jar
解决方法，要在project build path中先移除JRE System Library，再添加库JRE System Library，之后就可以了。