Question

Does this line:

List params = (List) hashMap.get(key);

create a new list, or just appends it to the list?

Here is how I use the code:

ParameterCache cache = ParameterCache.getInstance();
        HashMap hashMap = cache.getAllParameters(ParameterCodeConstants.PARAMETER_DORF_REGION, false);
        ArrayList regionIdList=new ArrayList();
        Set keys = hashMap.keySet();
        Iterator it = keys.iterator();
        while (it.hasNext()) {
            BigDecimal key = (BigDecimal) it.next();
            List params = (List) hashMap.get(key);
            if (params != null && params.size() > 0) {
                ParameterDTO paramDTO = (ParameterDTO) params.get(0);

                String textValue = paramDTO.getParameterTextValue();
                if(textValue.equals(region_id)){
                    regionIdList.add(paramDTO.getRegion());
                }

            }

        }

Answer 1

does this line create a new list or just appends to the list

List params = (List) hashMap.get(key);

None of this – only an assignment is taking place here. The value associated with key in this map is supposed to be a reference to an existing List object (or null), and this is returned by get. This reference is then assigned to params.

Since the local variable params did not exist prior to this declaration, there is no list to append anything to anyway.