是否可以在不同步关键字的情况下解决此代码？

我们可以使用ConCurrentHashMap或更好的带有同步关键字的HashMap（用于方法）吗？
或者更好的带有同步关键字（用于方法）的ConCurrentHashMap（用于迭代）？

这是临界区代码，读取器线程获取统计信息并减少值时（如果值为零，则删除统计信息，但并行写入器线程可能会产生值）。如何正确解决这个问题？

     Statistic statistic = data.get(id);
        if (statistic != null) {
            statistic.dec();

            if (statistic.getValue() <= 0) {
                data.remove(id);
           }

public class Main {

    private static final Map<Long, Statistic> data = new ConcurrentHashMap<>();

    public static void main(String... args) throws IOException {
        new Thread(() -> todoRunInWriterThread(1L)).start();
        new Thread(() -> todoRunInReaderThread(1L)).start();

        System.in.read();
    }

    //Many writers write some statistics
    private static void todoRunInWriterThread(long id) { 
        Statistic statistic = data.get(id);
        if (statistic == null) {
            statistic = new Statistic();
            data.put(id, statistic);
        }

        statistic.inc();
    }

    //Many readers read statistic and decrement value, 
    //if statistic value is zero (remove statistic)
    private static void todoRunInReaderThread(long id) {
        Statistic statistic = data.get(id);
        if (statistic != null) {
            statistic.dec();

            if (statistic.getValue() <= 0) {
                data.remove(id);
            }
        }
    }

    public static class Statistic {
        private AtomicLong value = new AtomicLong(0);

        public long getValue() {
            return value.longValue();
        }

        public void inc() {
            value.incrementAndGet();
        }

        public void dec() {
            value.decrementAndGet();
        }
    }
}