Lab 9 FAQ

The visualizer opens but Compute shows nothing / an error

Compute constructs your Lab9DFS, Lab9BFS, or Lab9Dijkstras and reads the order off of it. If a method still returns null, or anything throws, the page reports that instead of an order. Implement the method (or fix the exception), then stop and re-run Main. Refreshing the page is not enough, since the running program still has your old code.

“Address already in use” when running a visualizer

An earlier run of Main is still serving on port 4567. Stop that run in IntelliJ and try again.

The browser didn’t open automatically

The program prints the URL it is serving at (for example http://localhost:4567/). Open that in any browser.

For Dijkstra’s: distTo is wrong for one node but the rest are right

Make sure you set distTo[v] and edgeTo[v] and call changePriority every time a relaxation succeeds. Missing any one of the three gives confusing, partly-correct results.

Can’t find Javalin

It comes from library-fa26. Make sure the library is attached to your IntelliJ project as described in the Assignment Workflow Guide.