System.getProperty

os.name                Operating system name  
os.arch                Operating system architecture  
os.version            Operating system version  
file.separator            File separator ("/" on UNIX)  
path.separator            Path separator (":" on UNIX)  
line.separator Line separator ("\n" on UNIX)
user.name            User's account name  
user.home            User's home directory  
user.dir                User's current working directory