Creating a unique timestamp in Java

Question

I need to create a timestamp (in milliseconds) in Java that is guaranteed to be unique in that particular VM-instance. I.e. need some way to throttle the throughput of System.cu

Answer 1

You can use System.nanoTime() for better accuracy

Although I tried below and each time it gives different values, it probably is not guaranteed to be unique all the time.

public static void main(String[] args) {
        long time1 = System.nanoTime();
        long time2 = System.nanoTime();
        long time3 = System.nanoTime();
        System.out.println(time1);
        System.out.println(time2);
        System.out.println(time3);
    }

Another way is to use AtomicInteger/AtomicLong classes for unique numbers if the time is not important for you and you just need unique number, this probably is a btter choice.