如何从结果集中创建多个键值哈希图

Question

I would like to create multiple hashmaps from a resultset.

The final result should be something like below;

{
  slot_name = recommend,
  data = 7,
},
{
  slot_name = service,
  data = Good,
},
{
  slot_name = staff,
  data = Great,
},

I tried as below:

HashMap<String, String> data = new HashMap<String, String>();

while (resultSet.next()) {
    data.put("slot_name", resultSet.getString("name"));
    data.put("data", resultSet.getString("param_value"));
}

But when I printout the value of the hashmap, I get one record as below System.out.println(data);

{
  slot_name = staff,
  data = Great,
}

How can I achieve this? Someone assist, thank you

Answer 1

I would recommend to have a list and create a model class(instead of HashMaps) for "slot_name" and "data". Inside loop, construct object and add to the list. The reason, you are not getting as expected, is because, HashMap will have unique keys. So, for the same key when the value is again added, it will get updated.

class YourModel {
    String slotName;
    String data;
}

// inside loop
list.add(new YourModel(resultSet.getString("name"), resultSet.getString("param_value"));

Answer 2

A HashMap is a key value store. If you put the same key more than once, previous will be overwritten. This is the reason you saw only the last entry in the output.

if you want multiple maps, well create multiple ones. Eg.,

List<HashMap<String,String> maps = new ArrayList();
while (resultSet.next()) {
    HashMap<String, String> data = new HashMap<String, String>();
    data.put("slot_name", resultSet.getString("name"));
    data.put("data", resultSet.getString("param_value"));
    maps.add(data);
}