Product Version = NetBeans IDE 8.2 (Build 201609300101)
Operating System = Windows 10 version 10.0 running on amd64
Java; VM; Vendor = 1.8.0_101
Runtime = Java HotSpot(TM) 64-Bit Server VM 25.101-b13

Reproducibility: Happens every time

STEPS:
  * Edit a java project
  * Select a subexpression
  * Choose Refactor | Introduce | Variable (ALT+SHIFT+V)
  * Begin typing a variable name like "newvalue" or "intake"
  * Get as far as a reserved word like "new" or "int"

ACTUAL:
     red alert appears "name is not a valid java identifier" and OK button is disabled, but subsequent typing does not re-enable the OK button.  


EXPECTED:
    Subsequent typing re-enables the OK button and  new variable can introduced

Workaround: introduce it with another name and Refactor - Rename it to the desired name.

Example code:

package javaapplication25;

public class JavaApplication25 {
    public static void main(String[] args) {
       double z = (2.0+(2.0 * 3.0));
    }
    
}

Select '(2.0 * 3.0)' and press ALT+SHIFT+V.