It just doesn't work. Lots of known classes don't present anything.
I also tried this as I assumed it was searching all symbols, but it looks like it's only searching artifacts. Once you're into an artifact you get a search within that.
The keyboard navigation on the search doesn't work (pressing enter closes the results, doesn't navigate), and I find a search over artifacts to be too limiting for my use-case, but I guess it's not wrong.
I think I was extra confused because the HN title says it searches "packages" so I assumed that was what it was doing (in a java sense, where a package is the classes inside a library).
Yes, it's searching artifacts. Unfortunately searching symbols is not feasible until I have a larger budget. (Probably need TBs of index)
The keyboard navigation doesn't work yet, will fix in the next release.
2. The homepage requires you to choose an artifact/package first. Click "java.base" and then you can find SimpleDateFormat with the "search" field on the subsequent page.