find out the execution time of a block of code or whole program

ExecutionTimer.java

public class ExecutionTimer {
    private static long startTime;

    static {
        startTime = -1;
    }

    public static void startTimer() {
        startTime = System.currentTimeMillis();
    }

    public static String getTimeFromMillis(long millis) {
        String time = "";
        long seconds = millis / 1000;
        long minutes = seconds / 60;
        long hours = minutes / 60;
        long days = hours / 24;
        long months = days / 30;
        long years = months / 12;

        if (years > 0) {
            time += years + " year" + (years > 1 ? "s " : " ");
        }

        if (months > 0) {
            long mnths = (months % 12);
            if (mnths > 0) {
                time += mnths + " month" + (mnths > 1 ? "s " : " ");
            }
        }

        if (days > 0) {
            long dys = (days % 30);
            if (dys > 0) {
                time += dys + " day" + (dys > 1 ? "s " : " ");
            }
        }

        if (hours > 0) {
            long hrs = (hours % 24);
            if (hrs > 0) {
                time += hrs + " hour" + (hrs > 1 ? "s " : " ");
            }
        }

        if (minutes > 0) {
            long mins = (minutes % 60);
            if (mins > 0) {
                time += mins + " minute" + (mins > 1 ? "s " : " ");
            }
        }

        if (seconds > 0) {
            long secs = (seconds % 60);
            if (secs > 0) {
                time += secs + " second" + (secs > 1 ? "s " : " ");
            }
        }

        time += (millis % 1000) + " millis";

        return time;

    }

    public static String stopTimer() {
        if (startTime == -1) return "please start the timer";
        return getTimeFromMillis(System.currentTimeMillis() - startTime);
    }

    public static void main(String[] args) {
        System.out.println(getTimeFromMillis(System.currentTimeMillis()));
    }
}