参考网址：http://*.com/questions/860187/access-restriction-on-class-due-to-restriction-on-required-library-rt-jar
There's another solution that also works. I found it on this forum:
1、Go to the Build Path settings in the project properties.
2、Remove the JRE System Library
3、Add it back; Select "Add Library" and select the JRE System Library. The default worked for me.
This works because you have multiple classes in different jar files. Removing and re-adding the JRE lib will make the right classes be first