Automatically replacing with var using IntelliJ

Question

I'm migrating some pre Java 10 code and I'm wondering if IntelliJ offers a way to automatically refactor the code to replace the variable declarations that uses the actual type with var wherever it's possible.

The code is full of stuff like:

String status = "empty";
BigDecimal interest = BigDecimal.ZERO;
List<Future<Boolean>> results = es.invokeAll(tasks);
LocalDate start = LocalDate.of(2020, 1, 1);

And I would prefer:

var status = "empty";
var interest = BigDecimal.ZERO;
var results = es.invokeAll(tasks);
var start = LocalDate.of(2020, 1, 1);

I already looked in IntelliJ's settings (Code Style/Inspections) and couldn't find anything.

Answer 1

1. Go to File | Settings, there select Editor | Inspections, then under Java | Java language level migration aids | Java 10.

2. Right click on Local variable type can be omitted and select Weak Warning or similar.

3. Move Your cursor onto any of those warnings in Your code (highlighted grey), open quick fix context help (alt+enter), at Replace explicit type with 'var' move to the right and select Fix all 'Local variable type can be omitted' problems in file

Thanks for @olga-klisho for the idea (in comments)

Answer 2

I'm using IntelliJ IDEA 2021.3.2, but don't think the setting is new.

I've been struggling with this one myself.

It seems that the first time to install IntelliJ locally, by default, it will fall back to using traditional defining of variables (i.e. String s = new String();)

How I managed to change it into using var is after I declared something, for example new String(), either I pressed ⌥ Alt/Option+Enter to declare a variable for that declaration or by using ⌘ Command+⇧ Shift+V shortcut (I'm using Mac and classic Intellij key mapping, so YMMV) which activates declaration of a variable, this would show as follows:

As you see, it suggest to hit that key combination shortcut or clicking on the settings button that would open a pop up like this one:

Make sure you have Declare var type selected and you should be good to go.