You can't use <, >, |, && or ||, as those are not part of the commands. They are operators in your shell. Either do the file redirection yourself (using ss' getOutputStream() method), or execute the command through a shell. I'm not sure how to do it, but most shells (like bash) has an option to have it run another command.
Also, please read Please When Runtime.exec() won't before continuing. It'll help you prevent problems like hanging processes.