i want to print the username of the users that can only log in into the system not all the users not the system users.. and i want to do it through the java code as i want it in my project how can we do that?

You don't say what you use for "login" users. Is it /etc/passwd? NIS? LDAP?

Assuming /etc/passwd you can look at various fields to determine information about the users.

Type "man 5 passwd" to see the man page that describes the password file for what the various fields contain.

"system" users are usually those below UID 500 but this isn't guaranteed. Some "system" users (most notably "root") can also login. You might try excluding any user that has "/sbin/nologin" for the shell field. There is no hard an fast rule for "login" vs "system" user. It depends much on what you define.

I love your use of the English language. Providing you do something other then voice your wants.

google key phrase
"java parse passwd file Linux system" brought up some interesting methods.

Good Luck!