CODEWITHSUNDEEP
javacomparator
Shubham Pathak
Shubham Pathak

Reputation: 155

comparison of value on basis of key in list of maps

I have a map of string to String, and I want to sort the maps based on thier value for the kay F, but my code fails doing so. please advise.

    Map<String, String> h = null;
    Map<String, String> h1 = null;
    Map<String, String> h2 = null;
    listSummaryMap = new ArrayList<Map<String, String>>();

    h = new HashMap<String, String>();
    h.put("SUCCESS", "27");
    h.put("TOTAL_HOTELS", "86");
    h.put("F", "86");
    h.put("RESERVATION_MODE", "86");
    h.put("PARTNER_NAME", "86");

    h1 = new HashMap<String, String>();
    h1.put("SUCCESS", "27");
    h1.put("TOTAL_HOTELS", "86");
    h1.put("F", "36");
    h1.put("RESERVATION_MODE", "86");
    h1.put("PARTNER_NAME", "86");

    h2 = new HashMap<String, String>();
    h2.put("SUCCESS", "27");
    h2.put("TOTAL_HOTELS", "86");
    h2.put("F", "28");
    h2.put("RESERVATION_MODE", "86");
    h2.put("PARTNER_NAME", "86");

    listSummaryMap .add(h);
    listSummaryMap .add(h1);
    listSummaryMap .add(h2);


    Collections.sort(listSummaryMap , new Comparator<Map<String, String>>() {
        @Override
        public int compare(Map<String, String> o1, Map<String, String> o2) {
            return o2.get("F").compareTo(o1.get("F"));
        }
    });

Upvotes: 1

Views: 79

Answers (3)

CodingNagger
CodingNagger

Reputation: 1538

You forgot to add the maps to your list and the map h3 is never initialized. That taken apart your code already works as is but sorts the maps from the highest id to the lowest. If you change your comparison line to that:

Collections.sort(listSummaryMap , new Comparator<Map<String, String>>() {
    @Override
    public int compare(Map<String, String> o1, Map<String, String> o2) {
        return o1.get("F").compareTo(o2.get("F"));
    }
});

Then it will sort your maps by "F" from the lowest to the highest value.

Hope it helps

Upvotes: 0

Jekin Kalariya
Jekin Kalariya

Reputation: 3507

Need to convert String to integer first and then compare will work like this.

Collections.sort(listSummaryMap , new Comparator<Map<String, String>>() {
            @Override
            public int compare(Map<String, String> o1, Map<String, String> o2) {
                Integer a=Integer.parseInt(o2.get("F"));
                Integer b=Integer.parseInt(o1.get("F"));
                return b.compareTo(a);
            }
        });

Upvotes: 0

Eran
Eran

Reputation: 393846

Convert the Strings to Integers and compare as Integers :

    public int compare(Map<String, String> o1, Map<String, String> o2) {
        return Integer.valueOf(o2.get("F")).compareTo(Integer.valueOf(o1.get("F")));
    }

This is assuming the "F" key is always present in the Maps, and its value can always be parsed to an Integer.

BTW, I don't see where you add the Maps to listSummaryMap. Did you forget to include that code in your question?

Upvotes: 2

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