问ConcurrentHashMap保证

EN

class MyClass implements Flushable {
   private volatile ConcurrentHashMap<Integer, Object> hashMap = ...

   public void add(int id, Object value) {
      hashMap.put(id, value);
   }

   @Override
   public void flush() throws IOException {
      hashMap.foreach((k, v) -> ...)
      hashMap.clear();
   }

}