how to build project using ant in eclipse

[vijay mishra]

Hi,
i have eclipse 3.2. i imported project in eclipse using right
click and import existing project to the workspace and then i open
build.xml file run as ant build its running successfully but not
generating the jar file.

i changed some java code kept loger on that and that changes in not
comming when i am runing the application. please suggess me what to so
to solve this project.

Thanks in advance vijay mishra.