In the not so distant past, Jetbrains updated IntelliJ to preselect an auto-complete suggestion for you. This was painfully obvious when writing if/else blocks in Groovy where the 'else' would be changed to something completely different. To their credit, Jetbrains at least had the foresight to allow us to disable this. So, if you're suffering from unwanted code changes while writing code here's how to disable it:
* Open up preferences in IntelliJ
* In the project settings search box (top of setting window) type in 'code completion'
* Select 'code completion' from the list
* In the settings window on the right for the option 'Preselect the first suggestion:' choose 'Never'.
* Click the 'OK' or 'Apply' button.
That's it! Your blood pressure should go down at least 10 points...