Calling a node.js script from java using ProcessBuilder in mac

I am very much new to mac and its directory structure.

I have a node.js script on my desktop and the path to it is: /Users/username/Desktop/webserver

I would like to run this script(Along with an argument) within java using ProcessBuilder in Mac OSX.

In windows using Runtime, i would do something like:

String [] env=null;
String[]callAndArgs= {"node","server.js",argument};

Process p = Runtime.getRuntime().exec(callAndArgs,env,
new java.io.File("Path to my server.js file"));

BufferedReader stdInput = new BufferedReader(new 
InputStreamReader(p.getInputStream()));//getting the input

BufferedReader stdError = new BufferedReader(new 
InputStreamReader(p.getErrorStream()));//getting the error

interface_name = stdInput.readLine();//reading the output

How can I accomplish the same in mac, as when I input the /Users/username/Desktop/webserver as path to my node.js script, I get an error saying

java.io.IOException: error=2, No such file or directory

Any help would be really appreciated.

Thanks a lot in advance.