Detect internet Connection using Java

i googled      How Detect internet Connection using Java?

and found this code

try {

            Process p1 = java.lang.Runtime.getRuntime().exec("ping www.google.com");

            System.out.println(p1.waitFor());

// return 0(zero) if internet is availble

        }

catch (Exception e)

{

// caught exception

        }

It is working fine in windows.

How change above code so that it works for mac??

Thnax in advance