I need to gather some statistics in my software and i am trying to make it fast and correct, which is not easy (for me!)

first my code so far with two classes, a StatsService and a StatsHarvester

public class StatsService
{
private Map<String, Long>   stats   = new HashMap<String, Long>(1000);

public void notify ( String key )
{
    Long value = 1l;
    synchronized (stats)
    {
        if (stats.containsKey(key))
        {
            value = stats.get(key) + 1;
        }
        stats.put(key, value);
    }
}

public Map<String, Long> getStats ( )
{
    Map<String, Long> copy;
    synchronized (stats)
    {
        copy = new HashMap<String, Long>(stats);
        stats.clear();
    }
    return copy;
}
}

this is my second class, a harvester which collects the stats from time to time and writes them to a database.

public class StatsHarvester implements Runnable
{
private StatsService    statsService;
private Thread          t;

public void init ( )
{
    t = new Thread(this);
    t.start();
}

public synchronized void run ( )
{
    while (true)
    {
        try
        {
            wait(5 * 60 * 1000); // 5 minutes
            collectAndSave();
        }
        catch (InterruptedException e)
        {
            e.printStackTrace();
        }
    }
}

private void collectAndSave ( )
{
    Map<String, Long> stats = statsService.getStats();
    // do something like:
    // saveRecords(stats);
}
}

At runtime it will have about 30 concurrent running threads each calling notify(key) about 100 times. Only one StatsHarvester is calling statsService.getStats()

So i have many writers and only one reader. it would be nice to have accurate stats but i don't care if some records are lost on high concurrency.

The reader should run every 5 Minutes or whatever is reasonable.

Writing should be as fast as possible. Reading should be fast but if it locks for about 300ms every 5 minutes, its fine.

I've read many docs (Java concurrency in practice, effective java and so on), but i have the strong feeling that i need your advice to get it right.

I hope i stated my problem clear and short enough to get valuable help.