not to accessible duu to rt.jar

This generally happens when the java security file is tampered with or has additional file in the JRE home folder
If you have recently changed anything there, this is caused.
Go to JAVA_HOME/\jre\lib\security and see if you have jssecert file
copy it temporarily to some other location, now refesh your Eclipse java project, go to Project properpties>build path>.. remove JRE system library and add it again.
This should give you access again.