Thread-Safe Integer Sequence
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&lt;Class,AtomicInteger&gt; mapper = new ConcurrentHashMap&lt;Class,AtomicInteger&gt;();

    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.