My goal is to run SVN commands from java for one of my requirements, for the same i have already installed TortoiseSVN command line tool. Added the appropriate path\"C:/Prog
It's because you're not using ProcessBuilder correctly. The Javadocs are pretty clear cut.
You can't pass the --version argument as part of the process name you're trying to invoke; that's not the filename of the process. Behind the scenes you're exec'ing a process directly - there's no shell involved.
ProcessBuilder svnProcessBuilder = new ProcessBuilder("svn", "--version");