multithreading - Sequence Generator in Java for Unique Id

Question

I am planning to write a sequence generator which will be used in my REST resource implementation class during post to generate unique id. Since every post request is handled by separate thread, I made the variable volatile and method synchronized. I don't have option to use sequences or something which traditional RDBMS provides.

public class SequenceGen {
    volatile static int n = 0;  
    public synchronized int nextNum(){
        return n++;
    }   
}

this is what I have so far, and planning to create a variable of SequenceGen in my REST Implementation. My actual question is will it break somewhere ? I tested with two threads and I dont see any value repeated.

Answer 1

It will work, however AtomicInteger is an built in type that is perfect for your use case.

AtomicInteger seq = new AtomicInteger();
int nextVal = seq.incrementAndGet();