How to sort a list of maps on key in Java?

Question

I try to sort a Linked list of HashMaps by key

Wanted output:

[{Addres=Astreet, Name=Aron}, {Addres=Bstreet, Name=Bernie},{Addres=Cstreet, Name=Carol}]

  //Making Contacts

        HashMap contact1 = new HashMap();
        HashMap contact2 = new HashMap();
        HashMap contact3 = new HashMap();


        contact1.put("Name", "Bernie");
        contact1.put("Addres", "Bstreet");


        contact2.put("Name", "Aron");
        contact2.put("Addres", "Astreet");


        contact3.put("Name", "Carol");
        contact3.put("Addres", "Cstreet");


   //Making ContactBook

        LinkedList contactBook = new LinkedList();

        contactBook.add(contact1);
        contactBook.add(contact2);
        contactBook.add(contact3);


        System.out.println(contactBook);

Don't use `Map` but your own `class`, which has **instance** fields for `Addres` and `Name` — Lino, Mar 13 '20 at 12:13
I'd take a look at https://docs.oracle.com/javase/8/docs/api/java/util/Comparator.html — SpaceCowboy, Mar 13 '20 at 12:13
Does this answer your question? [How to sort Map values by key in Java?](https://stackoverflow.com/questions/922528/how-to-sort-map-values-by-key-in-java) — akuzminykh, Mar 13 '20 at 12:13
@akuzminykh I think Op wants to sort their `LinkedList` not the `HashMap`s themselves — Lino, Mar 13 '20 at 12:15

score 1 · Accepted Answer · answered Mar 13 '20 at 12:18

What you want to do is create a POJO that represents these entries and store them in a List. Then you can sort that list based on criteria like name or address.

        class Person {

            private final String name;

            private final String address;

            Person(String name, String address) {
                this.name = name;
                this.address = address;
            }

            public String getName() {
                return name;
            }

            public String getAddress() {
                return address;
            }

            @Override
            public String toString() {
                return String.format("name=%s, address=%s", name, address);
            }
        }

        List<Person> people = new ArrayList<>(Arrays.asList(
             new Person("Bernie", "Bstreet"),
             new Person("Aron", "Astreet"),
             new Person("Carol", "Cstreet")
        ));

        List<Person> sortedByName = people.stream()
                .sorted(Comparator.comparing(Person::getName))
                .collect(Collectors.toList());

        List<Person> sortedByAddress = people.stream()
                .sorted(Comparator.comparing(Person::getAddress))
                .collect(Collectors.toList());

How to sort a list of maps on key in Java?

1 Answers1