Why should var keyword not be used in an instance and global variable declaration in Java 10

Question

class Demo3 {
  
    // instance variable
    var x = 50;
    public static void main(String[] args)
    {
        System.out.println(x);
    }
}

Reference: https://www.geeksforgeeks.org/var-keyword-in-java/

Answer 1

You don't. The var keyword can only be used within a method scope while also being initialized immediately. Hence, instance variables can not be type inferred.

Answer 2

var can only be used for local variables. fields etc. were explictly excluded, see JEP 286.

In an Update on JEP 286, Java Language Architect Brian Goetz expressed a strong opinion about using it for fields:

"[...] is fields -- but applying type inference there would be foolish."