Say I have a below list
full_list
ID NAME
1 Apple
1 Banana
2 Carrot
1 Mango
2 Spinach
3 BMW
3 Opal
With this single list, I want to create a grouped list based on column ID like below
fruits_list veggies_list cars_list
ID NAME ID NAME ID NAME
1 Apple 2 Carrot 3 BMW
1 Banana 2 Spinach 3 Opal
1 Mango
I was trying to do it with Arraylist<ArrayList<CustomObject>>. But it is adding more complexity to the code. Am I doing it wrong? Is there any cleaner way to do this?
PS: Data incoming is not fixed. I cannot define lists explicitly with conditions (i.e. if(id==1), if(id==2) etc). This shall be done dynamically based on incoming data.
Thanks all for your answers. As @Mauron advised, I used Collectors.groupingby and it saved literally 20 lines of sorting code.
After some research I found how to list all keys in map here
So here is the solution I was looking for
//Create a grouped map using Collectors.groupingBy
Map m = itemslist.stream().collect(Collectors.groupingBy(ShipmentItemsModel::getLrid));
//Make an ArrayList of keys
ArrayList<Integer> keys = new ArrayList<>(m.keySet());
//Use enhanced for loop (foreach) to go through each key in order to create list of items each key has.
//(In Layman terms: It will create small lists based on keys)
for (int singlekey: keys) {
ArrayList<ShipmentItemsModel> values = new ArrayList<ShipmentItemsModel>();
values = (ArrayList<ShipmentItemsModel>) m.get(singlekey);
for (ShipmentItemsModel sortedmodel: values) {
System.out.println("Key/ID :"+singlekey+" and values :"+sortedmodel.getProductname());
}
}
So final output will be like this
Key/ID :1 and value :Apple
Key/ID :1 and value :Banana
Key/ID :1 and value :Mango
Key/ID :2 and value :Carrot
Key/ID :2 and value :Spinach
Key/ID :3 and value :BMW
Key/ID :3 and value :Opal
I appreciate all the answers. Thanks all once again.