I need to go over a not distinct list and count distinct each element in the list.

for example:

Object XXX { 

     int id;

     String type;

}

XXX:

id type

1    A

2    B

3    A

4    C

5    C

The rule should be activated per type and give as a result the count of each type:

A 2

B 1

C 2

Thanks