Okay, this question was a year ago but I recently got this problem as well.
So what I did :
- Update tomcat 7 to tomcat 8.
- Update to the latest java (java 1.8.0_141).
- Update the JRE System Library in Project > Properties > Java Build Path.
Make sure it has the latest version which in my case is jre1.8.0_141
(before it was the previous version jre1.8.0_111)
When I did the first two steps it still doesn't remove the error so the last step is important. It didn't automatically change the build path for jre.