用Java和Excel进行批处理可获得不同的结果

Question

I need to batch elements that have similar client id (String type, but at the moment only numeric values, like "12345", "235134", etc.)

Map<String, List<Client>> _batched = new HashMap<String, List<Client>>();
for (Client c : _Clients)
{
    String id = c.getIdClient();
    List<Client> clients = _batched.get(id);
    if(_clients == null){
        clients = new ArrayList<Client>();
        _batched.put(id, clients);
    }
    clients.add(c);
}

The problem is that when I compare this function with the results of Excel ( =SUM(IF(FREQUENCY(C2:C618,C2:C618)>0,1)) ), then I get different results, ie 526 and 519.

Is something wrong with my code?

Answer 1

Your problem is here:

String id = c.getIdClient();
List<Client> _clients = _batched.get(id);
if(_clients == null){
    pois = new ArrayList<Client>();
    _batched.put(id, _clients);
}
_clients.add(c);

You create a new array into a variable called pois but then put the contents of the variable _clients into _batched . What happens with the value put into pois ?

I don't understand how that doesn't null pointer exception actually.