Access restriction: The type BASE64Decoder is not accessible due to restriction

在MyEclipse中编写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

解决方案1（推荐）：
只需要在project build path中先移除JRE System Library，再添加库JRE System Library，重新编译后就一切正常了。
解决方案2：
Windows -> Preferences -> Java -> Compiler -> Errors/Warnings ->
Deprecated and trstricted API -> Forbidden reference (access rules): -> change to warning