One way is to execute the default program to open the document through the shell.
On Windows:
Process p = Runtime.getRuntime()
.exec("rundll32 url.dll,FileProtocolHandler C:/Path/To/Word.doc");
p.waitFor();
System.out.println("Done.");
Mac:
Process p = Runtime.getRuntime().exec("open /Documents/word.doc");
From - http://www.rgagnon.com/javadetails/java-0014.html