Check https://beothorn.github.io/javaflame to see an example.

There are already some tools that render flamegraphs for java, but they are focused on measuring performance or require some other process running along with the application. They also record function calls, but do not record the arguments or return values from those functions.

I needed instead something to help understand and debug my applications that was better than adding breakpoints and slowly step over every call.

This is a simple java agent that renders a flamegraph on a html file, no extra dependencies or other processes involved. All you need is an extra argument passed to the JVM on the command line pointing to the java agent.

It calls toString on every parameter and return value of every function that is included on the filter, so I wouldn't use this outside your dev machine.