I am new in Blackberry. Can anyone help me out for following queries?
Blackberry applications are written in Java. They support Java ME as well as some additional blackberry specific APIs. Check out http://na.blackberry.com/eng/developers/javaappdev/overview.jsp
As for calling a web service, yes you can do that as well. Check out the Rapid Application development tutorial at: http://na.blackberry.com/eng/developers/rapidappdev/