Populating a list with data from database using myBatis takes up a lot of time

Question

I have a table with almost 60000 data in it and I am running a select statement using myBatis mapper files, after analysing the code in debug mode I found that the data from the database was coming into DataSource fairly quickly, it was taking time while storing it in the List.

Driver Code.

Map<Long, Some_Custom_Class> mp = new HashMap<>();
List<Some_Custom_Class> myVar = selectAllDataFromTable();
if(myVar != null){
 for(Some_Custom_Class cs: myVar){
    mp.put(cs.getId(), cs)
 }
}

Mapper File

<select id="selectAllDataFromTable" resultMap="VariableMap">
   select  * from myTable
</select>

<resultMap id="VariableMap" type="myPackage.Some_Custom_Class">
        <id property="VariableID" column="variable_id" />
        <id property="SecondID" column="Second_ID" />
        <id property="Tag" column="tag" />
</resultMap>

I need to speed up the data insertion process in the list, is there any way to do it? I know a way that but I am not sure if it is correct. The way is by using threads and maybe having 2-4views and letting those threads access those views in some range let's say 0-10000 and so on. The for loop doesn't take much time to loop through 60000 data, but speeding that up will be a secondary task. My goal is to populate the list in the fastest way possible, can someone help me with that.