//Взято из OpenSwing Framework. Работает замечательно.
Хотя под Линукс не проверял. Под Винду все OK




/**
* <p>Title: OpenSwing Framework</p>
* <p>Copyright: Copyright (C) 2006 Mauro Carniel</p>
*
* <p> This file is part of OpenSwing Framework.
* This library is free software; you can redistribute it and/or
* modify it under the terms of the (LGPL) Lesser General Public
* License as published by the Free Software Foundation;
*
* GNU LESSER GENERAL PUBLIC LICENSE
* Version 2.1, February 1999
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the Free
* Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
*/

public static void displayURL(String url) {
try {
if (url.toLowerCase().startsWith("file://"))
url = url.substring(7);
Object desktop = Class.forName("java.awt.Desktop").getMethod(
"getDesktop", new Class[0]).invoke(null, new Object[0]);
desktop.getClass().getMethod("open",
new Class[] { java.io.File.class }).invoke(desktop,
new Object[] { new java.io.File(url) });
} catch (Throwable ex1) {
if (!url.toLowerCase().startsWith("file://"))
url = "file://" + url;
boolean windows = false;
String os = System.getProperty("os.name");
if (os != null && os.startsWith("Windows"))
windows = true;

String cmd = null;
try {
if (windows) {
// cmd = 'rundll32 url.dll,FileProtocolHandler http://...'
cmd = "rundll32 url.dll,FileProtocolHandler " + url;
Process p = Runtime.getRuntime().exec(cmd);
} else {
// Under Unix, Netscape has to be running for the "-remote"
// command to work. So, we try sending the command and
// check for an exit value. If the exit command is 0,
// it worked, otherwise we need to start the browser.
// cmd = 'netscape -remote
// openURL(http://www.javaworld.com)'
cmd = "netscape -remote openURL(" + url + ")";
Process p = Runtime.getRuntime().exec(cmd);
try {
// wait for exit code -- if it's 0, command worked,
// otherwise we need to start the browser up.
int exitCode = p.waitFor();
if (exitCode != 0) {
// Command failed, start up the browser
// cmd = 'netscape http://www.javaworld.com'
cmd = "netscape " + url;
p = Runtime.getRuntime().exec(cmd);
}
} catch (InterruptedException ex) {
System.out.println(
"Error while showing local document (cmd='"
+ cmd + "':\n" + ex.getMessage());
ex.printStackTrace();
}
}
} catch (Exception ex) {
// couldn't exec viewer
System.out.println("Error while local document (cmd='" + cmd
+ "':\n");
ex.printStackTrace();
}
}
}

Infidel//Взято из OpenSwing Framework. Работает замечательно.
Хотя под Линукс не проверял. Под Винду все OK


//Пример использования функции для Windows
displayURL("file://" + "./build/out.xls");