Access restriction: The type JFrame is not accessible due to restriction on required library

使用eclipse开发工具在需要JFrame时， 提示无法解析继承的类名，提示

error:

Access restriction: The type JFrame is not accessible due to restriction on required library D:\java2sdk\jre\lib\rt.jar

 at com.hao123.HisJFrame.main(HisJFrame.java:13)
Exception in thread "main"

解决方法： 

Project -> Properties -> libraries， 先remove掉JRE System Library，然后再Add Library重新加入D:\java2sdk\jre\lib【我安装java目录】下面的 .jar 包。