i have made my project using netbeans. I want to create tar file , how is it done. I want to an executable file to be made, and source code zipped to be used to modufy program later without using netbeans. I am really confused, can a poject made in netbeans be modified without netbeans. I have seen that source files are kept in src folder in netbeans. and jar file is made in dist folder. Please help me manage my project.

If I am not mistaken Netbeans uses internally Apache Ant's format for its build.xml for building (compiling etc) projects, So if you are familiar on how to use Apache Ant, you may even use notepad to modify your code or any other IDE (for ex Eclipse) which allows you to import projects made with Ant.
As far as tar-ing your sources go, if you are on a Linux distro a simple man tar in a terminal will tell you how to create a tar archive, However if you are on Windows take a look here, But on windows I suggest you use Zip/Rar instead, cause I do not see any difference between the three(except for tar being a free software).
Check this tutorial on how to create an executable jar in Netbeans