Get system uptime in Java

Question

How can I determine how long (in milliseconds) a computer has been powered on?

Answer 1

In Windows, you can execute the net stats srv command, and in Unix, you can execute the uptime command. Each output must be parsed to acquire the uptime. This method automatically executes the necessary command by detecting the user's operating system.

Note that neither operation returns uptime in millisecond precision.

public static long getSystemUptime() throws Exception {
    long uptime = -1;
    String os = System.getProperty("os.name").toLowerCase();
    if (os.contains("win")) {
        Process uptimeProc = Runtime.getRuntime().exec("net stats srv");
        BufferedReader in = new BufferedReader(new InputStreamReader(uptimeProc.getInputStream()));
        String line;
        while ((line = in.readLine()) != null) {
            if (line.startsWith("Statistics since")) {
                SimpleDateFormat format = new SimpleDateFormat("'Statistics since' MM/dd/yyyy hh:mm:ss a");
                Date boottime = format.parse(line);
                uptime = System.currentTimeMillis() - boottime.getTime();
                break;
            }
        }
    } else if (os.contains("mac") || os.contains("nix") || os.contains("nux") || os.contains("aix")) {
        Process uptimeProc = Runtime.getRuntime().exec("uptime");
        BufferedReader in = new BufferedReader(new InputStreamReader(uptimeProc.getInputStream()));
        String line = in.readLine();
        if (line != null) {
            Pattern parse = Pattern.compile("((\d+) days,)? (\d+):(\d+)");
            Matcher matcher = parse.matcher(line);
            if (matcher.find()) {
                String _days = matcher.group(2);
                String _hours = matcher.group(3);
                String _minutes = matcher.group(4);
                int days = _days != null ? Integer.parseInt(_days) : 0;
                int hours = _hours != null ? Integer.parseInt(_hours) : 0;
                int minutes = _minutes != null ? Integer.parseInt(_minutes) : 0;
                uptime = (minutes * 60000) + (hours * 60000 * 60) + (days * 6000 * 60 * 24);
            }
        }
    }
    return uptime;
}