Stop watch using System.nano

StopWatch.java

package monkstone;

public class StopWatch {

    private long startTime, pausedTime;
    private boolean paused = true;

    public StopWatch() {
        startTime = System.nanoTime();
    }

    public StopWatch start() {
        startTime = System.nanoTime() - pausedTime;
        paused = false;
        return this;
    }

    public long time() {
        return paused ? pausedTime : System.nanoTime() - startTime;
    }

    public int millis() {
        return (int) (time() / 1_000_000);
    }

    public int second() {
        return (int) (time() / 1_000_000 / 60);
    }

    /**
     * @return Returns the current no of minutes as per the stopwatch
     */
    public int minute() {
        return (int) (time() / 60_000_000 / 60);
    }

    public int hour() {
        return (int) (time() / 3_600_000_000L);
    }

    public void pause() {
        pausedTime = System.nanoTime() - startTime;
        paused = true;
    }

    @Override
    public String toString() {
        return "start: " + startTime + ", pausedTime: " + pausedTime + ", paused: " + paused;
    }    
}