Sort arraylist which have different objects

Question

I am new to stackoverflow.

Here is my question

This is about Android. I am implementing recycler view which have heterogeneous layouts.I am passing a static data to it. So if its Layout A it takes object A data. If its Layout B it takes Object B data and so on.

Example :

List.add(new A("May 27",2,3000$));

List.add(new B("April 21",2,"Place1",2000$));

List.add(new c("March 20","from place","toplace",5000$));

My Question is how i can sort the Recyclerview based on the date that we have passed for each object. let say "March 20" comes first so it has to appear at top in the recyclerview and "May 27" should display last in the Recyclerview.

I can use Collections.sort() by passing the list and the implementation of comparator interface as second argument. by taking away the date field and inserting it into parent class D and making class A,B,C inherit Class D. but its not working in my case.

Class D {

    private String date;

    // getter and setter method

}

Class A extends D{}

Class B extends D{}

Class C extends D{}

IN RecyclerViewAdapter

//onCreateViewHolder()


//OnBindViewHolder()

//getiewType()


//Creating list of data

private ArrayList<Object> getData(){

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

        for(int i=0;i<=20;i++) {

            list.add(new A("MAY 23", 1, 3000$));

            list.add(new B("April27", 1, 2, 3400$));

            list.add(new C("New york" "March 28", 1000$, 2, 2));

        }


    Collections.sort(list, new Comparator<D>() {

        @Override
        public int compare(D l1, D l2) {

            SimpleDateFormat sdf = new SimpleDateFormat("MMM dd", Locale.ENGLISH);

            Date d1=null;
            Date d2= null;

            try {
                d1=sdf.parse(String.valueOf(l1.getDate()));

                 d2= sdf.parse(String.valueOf(l2.getDate()));

             } catch (ParseException e) {

                e.printStackTrace();
            }

            if(d1 != null && d1.after(d2)){

                return -1;

            }else{

                return 1;}
            }

        return 0;

##error "unexpected token" /// or if do something here it shows entire block ##as error :

Wrong in 2nd argument

Found : java.util.comparator(D)

required : java.util.comparator(Object)

    });

    return list;

}

can some one please help me on this question. Thanks in advance

If you can make ABC extend D then you can just have ABC implement a common interface that provides a date, then you just sort on date — Novaterata
– Novaterata, Commented Apr 16, 2017 at 3:18
Thanks for the quick response. can you please help me with the code that will help me more — Mohan
– Mohan, Commented Apr 16, 2017 at 3:30
@Mohan use this link ideone.com/Lz6VoC i added for only for one case do it for remaining classes. Its too much boiler plate not an ideal solution but hope it helps in this regard. — SmashCode
– SmashCode, Commented Apr 16, 2017 at 4:34
is there any simple way to do its too much code to go. Thanks for your help @smashcode — Mohan
– Mohan, Commented Apr 16, 2017 at 5:01
wrap code existing after a instanceof b to a method and pass class objects as parameter then there will be no need to write same code 3 times — SmashCode
– SmashCode, Commented Apr 16, 2017 at 5:04

Raman Sahasi · Accepted Answer · 2017-04-16 04:18:52Z

1

You should get your desired output if you're passing correct comparator. It should look like this:

Collections.sort(list, new Comparator<ListType>() {
    @Override
    public int compare(ListType l1, ListType l2) {
        return l1.getDate().compareTo(l2.getDate());
    }
});

If it doesn't work, then check whether you're setting date correctly. I see that here you're passing date as a String. Are you parsing it correctly while setting it as a date?

EDIT

You're not parsing your date correctly. To parse these dates

May 27
April 21
March 20

You should use:

...
SimpleDateFormat sdf = new SimpleDateFormat("MMM dd", Locale.ENGLISH);
...

edited Apr 16, 2017 at 4:18

answered Apr 16, 2017 at 3:28

Raman Sahasi

32k9 gold badges63 silver badges74 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Mohan Over a year ago

Yes i even did that by using "Simpledateformat" class and using "parse" method to return date object and wrote the sorting code but when i pass the comparator to collections as (Collection.sort(list,new ComparatorImp) it is not accepting

Raman Sahasi Over a year ago

@Mohan please edit your question and post come code.

Mohan Over a year ago

Yes i changed the parsing format but the error is still remain same

Mohan · Accepted Answer · 2017-04-16 15:37:53Z

0

Finally i got the answer here is my solution

Solution pass Object class in Comparator and type cast it to ClassD :)

private ArrayList getData(){

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



        list.add(new A("MAY 23", 1, 3000$));

        list.add(new B("April27", 1, 2, 3400$));

        list.add(new C("New york" "March 28", 1000$, 2, 2));




Collections.sort(list, new Comparator<Object>() {

    @Override
    public int compare(Object l1, Object l2) {

        SimpleDateFormat sdf = new SimpleDateFormat("MMM dd", Locale.ENGLISH);

        Date d1=null;
        Date d2= null;

        try {
            d1=sdf.parse(String.valueOf((D)l1.getDate()));

             d2= sdf.parse(String.valueOf((D)l2.getDate()));

         } catch (ParseException e) {

            e.printStackTrace();
        }

        if(d1 != null && d1.after(d2)){

            return 1;

        }else if(d!=null && d1.before(d2)){

            return -1;
        }else return 0;

} return list;

answered Apr 16, 2017 at 15:37

Mohan

331 silver badge9 bronze badges

1 Comment

eckes Over a year ago

Looks to me like all the parsing of string dates is not needed. If getDate returns a Date object.

Collectives™ on Stack Overflow

Sort arraylist which have different objects

Wrong in 2nd argument

Found : java.util.comparator(D)

required : java.util.comparator(Object)

2 Answers 2

3 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

Wrong in 2nd argument

Found : java.util.comparator(D)

required : java.util.comparator(Object)

2 Answers 2

3 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related