Source: http://stackoverflow.com/questions/18075343/java-project-in-eclipse-the-type-java-lang-object-cannot-be-resolved-it-is-ind
This is an annoying Eclipse Bug which seems to bite now and then. See http://dev-answers.blogspot.de/2009/06/eclipse-build-errors-javalangobject.html for a possible solution, otherwise try the following;
Clean the project (It will rebuild the buildpath hence reconfiguring with the JDK libraries)
OR
Delete and Re-import the project and if necessary do the above steps again.
The better cure is to try NetBeans instead of Eclipse :-)
or
The following steps could help: