android sort ArrayList according to a obj data

Question

My list

ArrayList<MyList> list = new ArrayList<MyList>();
 //        name    - order - info
list.add("Book ...", "1", "blah blah);
list.add("Book ...", "10", "blah blah);
list.add("Book ...", "11", "blah blah);
list.add("Book ...", "2", "blah blah);

I want to sort the list according to its position in the 2 second obj

Then I tried

Collections.sort(list);

List Calss

public class MyList implements Comparable<MyList> {

...

    @Override
    public int compareTo(@NonNull MyList content) {
        return Integer.parseInt(content.getOrder());
    }
}

alayor · Accepted Answer · 2017-02-17 05:30:23Z

3

You can pass a Comparator object to the sort method.

Collections.sort(list, new Comparator<MyList>() {
    @Override
    public int compare(MyList m1, MyList m2) {
        return m1.getOrder() - m2.getOrder();
    }
});

If you're using java 8 you could do this.

Collections.sort(list, (MyList m1, MyList m2) -> 
                                   m1.getOrder() - m2.getOrder()));

edited Feb 17, 2017 at 5:30

answered Feb 17, 2017 at 5:20

alayor

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1 Comment

Gavin Harris Over a year ago

Nice! This way you can do different Comparisons in different circumstances! Sweet!

Darshan Mistry · Accepted Answer · 2017-02-17 05:30:31Z

2

ArrayList<MyList> list = new ArrayList<MyList>();
     //        name    - order - info
    list.add("Book ...", "1", "blah blah);
    list.add("Book ...", "10", "blah blah);
    list.add("Book ...", "11", "blah blah);
    list.add("Book ...", "2", "blah blah);

    Collections.sort(list, new Comparator<MyList>() {
        @Override
        public int compare(MyList m1, MyList m2) {
            return m1.getOrder() - m2.getOrder();
        }
    });

now check your list is in ascending order.

answered Feb 17, 2017 at 5:30

Darshan Mistry

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Comments

GhostCat · Accepted Answer · 2017-02-17 05:15:42Z

1

You need a Comparator here.

That one compares two items, and returns -1, 0, or 1; if the first entry is smaller, equal, bigger than the second one.

But you should go one step further: it seems like you try to model certain data - then don't use a flat MyList list class. Create a class that really models your data; maybe a BookRecord; that has fields like String name, or int id.

answered Feb 17, 2017 at 5:15

GhostCat

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Comments

Gavin Harris · Accepted Answer · 2017-02-17 05:20:58Z

1

Make your compareTo method look like:

    public int compareTo(MyList o) {
        return this.getOrder() - o.getOrder();
    }

answered Feb 17, 2017 at 5:20

Gavin Harris

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