Is it possible to create an application that prevent users from running
certain applications for a certain period of time using java? Like when
a user logs in the pc, only applications that was allowed in his access
level would run. Thanks in advance :)

In my opinion that would be hard to impossible in a Java application - it would need to interact with the system at quite a low level and be immune from the user stopping it. There may well be other ways to do it, eg via Group Policies in Windows - try posting the question in the Microsoft Windows or Linux and Unix forums as approprate.