使用Desktop＃browse（URI）方法。它将在用户的默认浏览器中打开一个URI。

public static boolean openWebpage(URI uri) {
    Desktop desktop = Desktop.isDesktopSupported() ? Desktop.getDesktop() : null;
    if (desktop != null && desktop.isSupported(Desktop.Action.BROWSE)) {
        try {
            desktop.browse(uri);
            return true;
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    return false;
}

public static boolean openWebpage(URL url) {
    try {
        return openWebpage(url.toURI());
    } catch (URISyntaxException e) {
        e.printStackTrace();
    }
    return false;
}