How to sort a nested map by inner keys descending order and then by inner values in ascending order?

Question

I have a nested map Map<String, Map<String, Integer> for example

("Samsung", ("Note", 30))

("Samsung", ("Galaxy", 20))

("Apple", ("Iphone", 40))

I need to sort the map by inner key alphabetically in descending (in this example case - the model name)

and if two names are equal then I have to sort the inner values in ascending (in this case - the price).

My sorting by far is like this:

map.entrySet().stream.forEach(entry -> entry.getValue().entrySet().stream() .sorted(Comparator.comparing(Map.Entry::getKey, Comparator.reverseOrder()))

And I know I have to add .thenComparing(), but I don't know how to proceed next.

You want to sort data in descending order of Model name ; and if Madel name are same then on ascending order of price .. Right ? — Ajinkya, Jan 29 '20 at 10:23
@Ajinkya No, I think the model names don't have to be the same. — Методи Владимиров, Jan 29 '20 at 10:27
then on what basis do you have to sort these data ? on BrandName and Price ? — Ajinkya, Jan 29 '20 at 10:29
@Ajinkya I am telling you, first on brand name and then by their price. — Методи Владимиров, Jan 29 '20 at 10:32
This does not make any sense, sort based on two properties? Could you please elaborate on your question a bit more? — Mehrdad HosseinNejad Yami, Jan 29 '20 at 11:15
@MehrdadHosseinNejad If they key names are equal, then I must sort the values — Методи Владимиров, Jan 29 '20 at 11:18
What sort of structure would you like your final sorted data to be in? — DodgyCodeException, Jan 30 '20 at 10:18

Ajinkya · Answer 1 · 2020-01-29T17:04:50.320

0

You write a CustomComparator as Follows:

import java.util.*;

public int compare(Object obj1  , Object obj2){

        Map<String, Map<String, Integer> > map1 = (Map<String, Map<String, Integer>) obj1;
        Map<String, Map<String, Integer> > map2 = (Map<String, Map<String, Integer>) obj2;
        Map.Entry e1 = (Map.Entry)map1.entrySet();
        Map.Entry e2 = (Map.Entry)map2.entrySet();
        String brand1 = (String)e1.getKey();
        String brand2 = (String)e2.getKey();
        Map.Entry e3 = (Map.Entry)e1.getValue();
        Map.Entry e4 = (Map.Entry)e3.getValue();
        Integer price1 =(Integer) e3.getValue();
        Integer price2 =(Integer) e4.getValue();

        if(brand2.compareTo(brand1) != 0){
            return brand2.compareTo(brand1);
        }else{
            price1.compareTo(price2);
        }
      }
    }

This Compactor will sort data in descending order of brand name first And if two brand having same name then for that it will sort in ascending order of price .

You have to add your data in TreeMap as follows

Set data = new TreeSet(new CustomComparator()); //Add your data here in data object

edited Jan 29 '20 at 17:04

answered Jan 29 '20 at 10:45

Ajinkya

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@Методи Владимиров is sorting logic implemented here in CustomComaprator class is same as per your need ? – Ajinkya Jan 29 '20 at 10:47
@Ajinya I think yes, I just need to implement it to see and test. – Методи Владимиров Jan 29 '20 at 10:52
@Ajinya I don't know why, but I can't access and I don't have .getKey() method for map1 and map2, neither the value. – Методи Владимиров Jan 29 '20 at 11:02
1

@МетодиВладимиров you have import java.util.* – Ajinkya Jan 29 '20 at 11:08
Yes i have.., at the very top – Методи Владимиров Jan 29 '20 at 11:09
@МетодиВладимиров Sorry my bad Please try this updated code now. – Ajinkya Jan 29 '20 at 11:25
and now I am trying to place the custom class name inside .sorted(...) in the pipeline, but I get `expression expected` – Методи Владимиров Jan 29 '20 at 11:34
Lets Discuss in Chat : https://chat.stackoverflow.com/rooms/206852/man-ki-baat – Ajinkya Jan 29 '20 at 11:42
@МетодиВладимиров You have to create a TreeMap with CustomCmparator and add all data in that map It will get sorted automatically – Ajinkya Jan 29 '20 at 11:46
I can't my reputation is lower than 20 :( – Методи Владимиров Jan 29 '20 at 11:49
@МетодиВладимиров is your all data of Map object is stored inside a List? – Ajinkya Jan 29 '20 at 14:15
No it isn't. Actually it is a field property inside a class. – Методи Владимиров Jan 29 '20 at 16:34

How to sort a nested map by inner keys descending order and then by inner values in ascending order?

1 Answers1