Sorting Error: Hashmap<String, List<String>>

Question

I have a: Hashmap<String,List<String>> i want to sort it by Keys when i tried sorting it and cliked activity button my the emulator closes application. How i can fix it? My activity inside my application look like now:

I want to sort it like: 01,02,03,04,05 etc.

Here my code blocks:

InsidesActivity.class:

public class InsidesActivity extends AppCompatActivity {
    HashMap<String, List<String>> Insides_Categories;
    List<String> List_Items;
    ExpandableListView expandableListView;
    Expandible_List ExpListClass;
    Toolbar tb;
    int lastPosition = -1;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_insides);
        expandableListView = (ExpandableListView) findViewById(R.id.explist);


            Insides_Categories = DataProvider.getInfo();
            List_Items = new ArrayList<String>(Insides_Categories.keySet());

I tried this block:

//        List<Map.Entry<String,List<String>>> entries = new ArrayList<Map.Entry<String,List<String>>>(Insides_Categories.entrySet());
//        Collections.sort(entries, new Comparator<Map.Entry<String,List<String>>>() {
//            public int compare(Map.Entry<String,List<String>> l1, Map.Entry<String,List<String>> l2) {
//                return l1.getValue().get(0).compareTo(l2.getValue().get(0));
//            }
//        });

            ExpListClass = new Expandible_List(this, Insides_Categories, List_Items);
            expandableListView.setAdapter(ExpListClass);
        }
    }

@AyushKhare the IDE didnt throw an error. Just closed application when i tried join this Activity. — Halil Sahin
– Halil Sahin, Commented Aug 11, 2017 at 7:18
@shmosel then what should i do? Do you have an idea for me ? — Halil Sahin
– Halil Sahin, Commented Aug 11, 2017 at 7:23
Idea for what? All you've said is that you want to sort a map, which isn't possible. — shmosel
– shmosel, Commented Aug 11, 2017 at 7:24

Sagar Panchasara · Accepted Answer · 2017-08-14 16:03:59Z

Use LinkedHashMap to maintain your sorting order. HashMap doesn't keep order as data inserted.

public static void main(String[] args) {
    Map<String, List<String>> map = new LinkedHashMap<>();
    map.put("b", Arrays.asList("1", "2"));
    map.put("a", Arrays.asList("2", "1"));
    map.put("c", Arrays.asList("2", "1", "6"));
    map.put("d", Arrays.asList("2", "1", "5"));
    Stream<Entry<String, List<String>>> sorted = map.entrySet().stream().sorted(Map.Entry.comparingByKey());
    System.out.println("map:" + map);
    map = sorted.collect(new Supplier<Map<String, List<String>>>() {

        @Override
        public Map<String, List<String>> get() {
            return new LinkedHashMap<>();
        }
    }, new BiConsumer<Map<String, List<String>>, Entry<String, List<String>>>() {

        @Override
        public void accept(Map<String, List<String>> t, Entry<String, List<String>> u) {
            t.put(u.getKey(), u.getValue());
        }
    }, new BiConsumer<Map<String, List<String>>, Map<String, List<String>>>() {
        @Override
        public void accept(Map<String, List<String>> t, Map<String, List<String>> u) {
            // TODO
        }
    });
    System.out.println("map:" + map);
}

Halil Sahin · Accepted Answer · 2017-08-11 08:20:35Z

0

I solved my problem when i sorted my List like this;

List_Items = new ArrayList<String>(Insides_Categories.keySet());
Collections.sort(List_Items);

Now its looks like:

answered Aug 11, 2017 at 8:20

Halil Sahin

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