ubun2

Ok so I failed at installing java-jre and now when I load up my update manager it says "Software index is broken" and tells me to use "Synaptic' but when i do i get the same error that i get when i run "sudo apt-get install -f".  and that error is my question.  How can i reinstall java-jre?  This is killing my day.  Thxxx

I downloaded a rar file from the internet. When i tried to open using Archive Manager, it errored out saying rar file type is not supported. I checked 7Zip but couldn't find a install for it for ubuntu or linux. How to open rar format files in ubuntu? please help.