I have a list of custom object,

```
public class Assignmentsdata {

    String assignmentId;
    String teacherId;
    String groupName;
    String sectionId;
    String levelId;
    String startTime;
}

ArrayList<Assignmentsdata> list = new ArrayList<>();

```

> 
> lets say there are 20 elements in that list.
> 
> 
> 

Now I want to get the output which is a hashmap of startTime as a key and the Value would be a new HashMap of GroupID and a list of Assignments of those that had the same groupName.

**OutPut Example**

HashMap<startTime,HasMap<groupName,List> hashMap = new HashMap();

a little more insight about the problem: First I want to categorise based on startTime(Month) then i want to categorise based on groupName, Thanks in advance.

I have successfully categorised based on group name and created a map through below code:

```
 for( int i = 0; i<assignmentsdataArrayList.size();i++ ){
                if (hashMap.size()>0){
                    hashMap.get(assignmentsdataArrayList.get(i).getGroupName()).add(assignmentsdataArrayList.get(i));
                }else {
                    hashMap.put(assignmentsdataArrayList.get(i).getGroupName(),new ArrayList<Assignmentsdata>());
                    hashMap.get(assignmentsdataArrayList.get(i).getGroupName()).add(assignmentsdataArrayList.get(i));
                }
            }

```

**After that I am lost on how to categorise this hashmap based on the startDate and create a hashmap that would look like the above hashmap in the output heading.**