public static DBusConnection getConnection()

in dbus-java/src/main/java/org/freedesktop/dbus/connections/impl/DBusConnection.java [216:286]
55 lines of code
13 McCabe index (conditional complexity)

    public static DBusConnection getConnection(DBusBusType _bustype, boolean _shared, int _timeout) throws DBusException {
        switch (_bustype) {
            case SYSTEM:
                DBusConnection systemConnection = getConnection(() -> {
                    String bus = System.getenv("DBUS_SYSTEM_BUS_ADDRESS");
                    if (bus == null) {
                        bus = DEFAULT_SYSTEM_BUS_ADDRESS;
                    }
                    return bus;
                }, true, _shared, _timeout);
                return systemConnection;
            case SESSION:
                DBusConnection sessionConnection = getConnection(() -> {
                    String s = null;

                    // MacOS support: e.g DBUS_LAUNCHD_SESSION_BUS_SOCKET=/private/tmp/com.apple.launchd.4ojrKe6laI/unix_domain_listener
                    if (SystemUtil.isMacOs()) {
                        s = "unix:path=" + System.getenv("DBUS_LAUNCHD_SESSION_BUS_SOCKET");

                    } else { // all others (linux)
                        s = System.getenv("DBUS_SESSION_BUS_ADDRESS");
                    }

                    if (s == null) {
                        // address gets stashed in $HOME/.dbus/session-bus/`dbus-uuidgen --get`-`sed 's/:\(.\)\..*/\1/' <<<
                        // $DISPLAY`
                        String display = System.getenv("DISPLAY");
                        if (null == display) {
                            throw new RuntimeException("Cannot Resolve Session Bus Address");
                        }
                        if (!display.startsWith(":") && display.contains(":")) { // display seems to be a remote display
                                                                                 // (e.g. X forward through SSH)
                            display = display.substring(display.indexOf(':'));
                        }

                        try {
                            String uuid = getDbusMachineId();
                            String homedir = System.getProperty("user.home");
                            File addressfile = new File(homedir + "/.dbus/session-bus",
                                    uuid + "-" + display.replaceAll(":([0-9]*)\\..*", "$1"));
                            if (!addressfile.exists()) {
                                throw new RuntimeException("Cannot Resolve Session Bus Address");
                            }
                            Properties readProperties = FileIoUtil.readProperties(addressfile);
                            String sessionAddress = readProperties.getProperty("DBUS_SESSION_BUS_ADDRESS");
                            
                            if (StringUtil.isEmpty(sessionAddress)) {
                                throw new RuntimeException("Cannot Resolve Session Bus Address");
                            }

                            // sometimes (e.g. Ubuntu 18.04) the returned address is wrapped in single quotes ('), we have to remove them
                            if (sessionAddress.matches("^'[^']+'$")) {
                                sessionAddress = sessionAddress.replaceFirst("^'([^']+)'$", "$1");
                            }
                            
                            return sessionAddress;
                        } catch (DBusException _ex) {
                            throw new RuntimeException("Cannot Resolve Session Bus Address", _ex);
                        }
                    }

                    return s;

                }, true, _shared, _timeout);

                return sessionConnection;
            default:
                throw new DBusException("Invalid Bus Type: " + _bustype);
        }

    }