That was my first thought as well. I'll also add that it doesn't look like it would work as well in Java thanks to Java being much more verbose.

Given about 2 minutes of thought I'm leaning towards this being the wrong approach. The challenge with verbose languages is getting enough context on screen or in your head to think about the real problem; it's a pretty old problem and a lot of things have been tried, but not much has really worked. What I would like to see is something that hides more of the incidental complexity and lets you not think about it.

FWIW, the smalltalk browser _look_ ("hierarchical" selector blocks on top and content at the bottom) has been an available UI in java in eclipse for years, and IMO it's far better than the tree-ish browser on the side exactly because it helps with getting more context on screen