Java SE (Java Platform, Standard Edition)

Hello
I want to launch a pdf-file (from within the code) on the system default pdf-reader. Can I somehow retrieve the path to the default pdf-reader and use it like this:

String pdfReaderPath = retrievePDFreaderpath(); // ????
String filename = new String("E:\\Test.pdf");
String[ ] open = {pdfReaderPath , filename};

try {
Process proc = Runtime.getRuntime().exec(filename);
} catch (IOException e) {
e.printStackTrace();
}

Thank you!