number of values associated to a given value in an arraylistmultimap

number of values associated to a given value in an arraylistmultimap

ArrayListMultiMap<String,MyDataStructure> x = null;
x=x.create();
Now, how do I get the number of values that are associated to a gives key.
I tried this.
int count = x.get(key).size();
but this size return a dimension class instead of an int.