Steps

Analyse code

1. Click on Root Project
2. Click on "Analyse" -> "Inspect Code"
3. Select on "Whole Project"
4. Select on "Whole Project"
5. Check following:
6. Exclude "Properties Files" and "Spelling" categories
7. "Android" -> "Lint" -> "Correctness" -> "Obsolete Gradle Dependency" (all except comment for block)
8. "Android" -> "Lint" -> "Performance" -> "Obsolete SDK_INT Version Check" -> "Merge ressourcess from ... values"
9. "Android" -> "Lint" -> "Performance" -> "Useless parent layout" -> check it
10. "Android" -> "Lint" -> "Performance" -> "Unused resources" -> category -> file -> right click -> "Remove all unused declaration"
11. /!\ Be sur you do not use it, because you can use it programmatically!
12. "Java" -> "Accept suggested access level"
13. "Java" -> "Imports" -> "Unused import"
14. "Java" -> "Probable bug"

Reformat code

1. Click on Root Project
2. Click on "Code" -> "Reformat Code"
3. Select ONLY "Optimize imports"
4. Click on "Run"