FULL PRODUCT VERSION :
java version "1.8.0_101"
Java(TM) SE Runtime Environment (build 1.8.0_101-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.101-b13, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
OSX El Capitan - version 10.11.6

uname -a
Darwin SDGL149ca5171.local 15.6.0 Darwin Kernel Version 15.6.0: Thu Jun 23 18:25:34 PDT 2016; root:xnu-3248.60.10~1/RELEASE_X86_64 x86_64

A DESCRIPTION OF THE PROBLEM :
Regex replacement using Nashorn has different behavior than other javascript implementations.



STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Open up the `jjs` shell, and get the output of the following command:

"4005".replace(/\B(?=(\d{3})+(?!\d))/g, ",");

The output for nashorn is: "4,,005". Note the duplicate comma.

In the Rhino ScriptEngine, NodeJS, or any browser implementation of Javascript, the double comma doesn't exist.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
I would expect the output of the .replace() to be equal to "4,005", as it is in every other Javascript implementation.
ACTUAL -
The output of the replace contains a duplicate ","

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
    public static void main(String[] args) throws ScriptException {
        ScriptEngine scriptEngine = new ScriptEngineManager().getEngineByExtension("js");
        String replaceResult = (String) scriptEngine.eval("\"4005\".replace(/\\B(?=(\\d{3})+(?!\\d))/g, \",\")");
        if (!replaceResult.equals("4,005")) {
            throw new RuntimeException("Replace failed");
        }
    }
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
You can switch to use the Rhino ScriptEngine, which doesn't contain this error.


ScriptEngine scriptEngine = new ScriptEngineManager().getEngineByName("rhino");

Add this dependency if using maven:
        <dependency>
            <groupId>de.christophkraemer</groupId>
            <artifactId>rhino-script-engine</artifactId>
            <version>1.1.0</version>
        </dependency>