How to get Bukkit.jar file for plugin development

Hey all,

So I am a good programmer in Java and HTML and I have a sudden interest in MC server plugin development.
I have went through all I could and most of the reasearch shows that you need to improt an external Java source called Bukkit.jar into your project.
I went through all I could to try and find the file but it isnt shown any where and most of the links are not working(but most of my sources are from 2013-2015 so it's pretty outdated).

I am new tonthis community so could you all update me in what I missed and how will I be able to make a plugin and where can I find find the Bukkit.jar

Thank you.

Also sorry if this is the wrong section to post this question

EDIT by Moderator: merged posts, please use the edit button instead of double posting.