And what's wrong with :
public final class SDGIntIDGenerator {
private static final AtomicInteger sequence = new AtomicInteger(1);
private SDGIntIDGenerator() {}
public static int generate(){
return sequence.getAndIncrement();
}
}
Atomic Integer is thread safe.
Put private constructor so no instances can be made.
Only static methods means helper class => make class final.
Edit :
While @bowmore is correct you could want more generators for each class, you could do the following :
public final class SDGIntIDGenerator {
private static final ConcurrentHashMap<Class,AtomicInteger> mapper = new ConcurrentHashMap<Class,AtomicInteger>();
private SDGIntIDGenerator () {}
public static int generateId (Class _class) {
mapper.putIfAbsent(_class, new AtomicInteger(1));
return mapper.get(_class).getAndIncrement();
}
}
With this implementation you could ask an id for each class.
This is because the ConcurrentHashMap is also thread safe for some methods.
Important note : Your generator will reset himself after server restart so usage for generating an id for storing in database is a bad idea.
You could also just return the AtomicInteger.
It doesn't matter if you are using a lot of threads and every thread knows that instance of the AtomicInteger.
The AtomicInteger will stay threadsafe.
Footnote : Wrote in java 6, with higher java you could refactor the instantiation of the ConcurrentHashMap.
