How can I make the article headlines more clean in my homepage?

I have a simple webpage where I take notes on various things. I have a few "folders" (topics) and several "files" (articles) under them. My current homepage is like this:

For example java has class-design and collections and collectors and so on. I tried to separate the files with a dot between them but I think it is still needs quite an effort to distinguish single pages.

How can I make it more cleaner so that it is easier on the eyes to realise individual files under a topic?