The IntelliJ line of projects are fantastic for this. I can make the jumps around in multiple files and libraries to follow the flow. I can easily setup debug

The IntelliJ line of projects are fantastic for this. I can make the jumps around in multiple files and libraries to follow the flow. I can easily setup debugging, set breakpoints, and watch what values poorly named variables carry. It spots unused imports and variables in the code as well, which makes it easier to clean out cruft. I have heard good things about Visual Studio Code as well, but IntelliJ gets my money every time.