gzip: stdin: unexpected end of file -> problem in extracting jdk-7u55-linux-x64.tar.gz
Solution 1:
Please don't use sudo unless necessary. If you are extracting this into a directory you have access to, there's no need for sudo.
Anyway, the error you're getting is usually due to an incomplete download. The archive ends before the expected footer of the gzipped file. It will probably work fine if you just download it again.