While trying to understand the code, you may want to perform small refactorings, like renaming a variable or method using Refactor | Rename ⇧F6 (macOS) / Shift+F6 (Windows/Linux), Extract Method using ⌥⌘M (macOS) / Ctrl+Alt+M (Windows/Linux) to extract a method and giving it a meaningful name, or refactoring the code to a style you are more familiar with to make it easier for you to read and understand the code, for example using Intention Actions ⌥⏎ (macOS) / Alt+Enter (Windows/Linux). Playing with the code can help you verify your assumptions and improve your understanding. Remember though, that these changes are not meant to be committed. Revert them when you’re done!