CTS Android Automation via CI Tool

Question

I am trying to execute android CTS via this command: ./cts-tradefed run cts --shards ${no_of_devices}

When I execute a plain shell command from terminal it detects all the connected devices and executes test suite in parallel using all connected devices to execute tests. While when I try to call this shell command from Java code(locally) or CI server; it detects all devices but executes tests on (no_of_devices -1). The device that gets ignored is always the first device in the list. Confirmed that device itself is not a problem because if same device is not the first one in the list of devices, that device will be used for executing the tests.

My shell script looks like:

!#/bin/bash

./cts-tradefed run cts --shards 2 #say if I have two devices connected

The java code I use to execute the shell script is this:

public class Main {
    public static void main(String[] args) {

    ProcessBuilder pb = new ProcessBuilder("temp/run-cts-with-sharding.sh");
        try {
            Process p = pb.start();
            Thread.sleep(2000);
        BufferedReader reader = new BufferedReader(
                new InputStreamReader(p.getInputStream()));

            String line;

            while ((line = reader.readLine()) != null) {
                System.out.println(line);
            }

        } catch(Exception e) {
            System.out.println("Exception on pb.start(): " + e);
        }
    }
}