Plugin Help "Source not found"

Hallo.

So today I began my morning with some coding and what not, and I was revising some of my code. While I was, I was awestruck with a problem that I thought should be addressed.

So here is the problem:

Problem as a picture (open) Problem as a picture (close)

Picture:

Alternative:
If that doesn't work, click here.

I want to code and be able to see the source behind the code; however, I can't. How could I fix this?

 

@timtower how do I change that?
EDIT:
Before I restarted my Eclipse, I used to be able to access these classes

 

@maux
Could you fix the picture and the link (or is it just me?) and write what you have in your buildpath. Then please also add if the class file you tried to view is in a package of a jar in the build path or in the project.

 

@I Al Istannen Picture link: https://imgur.com/edit?deletehash=gh002CMlOoSWT8g
And also it's a package of a jar.

 

@maux
Well, if the class is in a jar file and the source is not packaged with it, eclipse just knows the class files and not the ".java" ones.
If it is your own code, add the Project as a dependency in the "Projects" tab instead of the generated jar in the "Libraries" one. Then you will be able to view the source.

If it isn't your code, you will need to decompile it. This can totally screw up the code, and it won't look that nice after it. You might want to try different decompilers at the same time to get a better grasp of what is happening. You might alos be not allowed to modify the code in any way.

 

Okay thanks
@I Al Istannen