How to sort an ArrayList on more than one field

Question

I have ArrayList<Item> itemList. The Class Item contains two fields: char firstLetter and char secondLetter.

If I wanted to sort itemList on firstLetter, the code would be

 Collections.sort(itemList, new Comparator<Item>() {
        @Override
        public int compare(Item o1, Item o2) {
            char order1 = o1.getFirstLetter();
            char order2 = o2.getFirstLetter();
            return Character.compare(order1,order2);
        }
    });

However, within the same sorting operation I want itemList also to be sorted according to secondLetter. So items that have the same value for firstLetter are sorted among them according to their value for secondLetter. How should the above code be modified?

Duplicate of [How to sort by two fields in Java?](https://stackoverflow.com/questions/4805606/how-to-sort-by-two-fields-in-java) — Zoe, Oct 14 '21 at 09:32

akhil nair · Accepted Answer · 2021-09-28T14:31:58.193

1

You can try this.

Collections.sort(itemList, new Comparator<Item>() {
    @Override
    public int compare(Item o1, Item o2) {
        char order1 = o1.getFirstLetter();
        char order2 = o2.getFirstLetter();

        char order3 = o1.getSecondLetter();
        char order4 = o2.getSecondLetter();

        String first = String.valueOf(order1)+String.valueOf(order3)
        String second= String.valueOf(order2)+String.valueOf(order4)

        return first.compareTo(second);
    }
});

An embedded solution should look like this:

Collections.sort(itemList, new Comparator<Item>() {
    @Override
    public int compare(Item o1, Item o2) {
        char order1 = o1.getFirstLetter();
        char order2 = o2.getFirstLetter();

        char order3 = o1.getSecondLetter();
        char order4 = o2.getSecondLetter();

        int compare = Character.compare(order1,order2);

        if(compare == 0){
            return Character.compare(order3,order4);
        } else {
            return compare;
        }
    }
});

edited Sep 28 '21 at 14:31

answered Sep 28 '21 at 13:27

akhil nair

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I don't even have to try it to know that this brilliant hack will work. I was looking for an embedded solution, but this certainly will do the job just as well. Thanks. – Red Knight Sep 28 '21 at 13:50
@RedKnight If this solution has helped you please accept and upvote it so that it can help others in the community. Thanks – akhil nair Sep 29 '21 at 06:33
Can't. My reputation is too low. – Red Knight Sep 29 '21 at 19:07
@RedKnight You can't upvote it but you can surely accept it. https://stackoverflow.com/help/someone-answers – akhil nair Sep 29 '21 at 20:53
You're right. Done. Your embedded solution looks great too. – Red Knight Sep 30 '21 at 06:44

How to sort an ArrayList on more than one field

1 Answers1