Sorting map according to user defined criteria?

Question

I have a map in which I want some values to be come on top.

HashMap<String,String> hm = new HashMap<String,String>(); 
hm.put("Phone Number","998291829");
hm.put("Address","12 A Street");
hm.put("Name","Robert Singh");
hm.put("Email","robert@gmail.com");
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I want Name and email as first and second entry,How can I do this.

Do you want the items to be sorted in the way they are inserted? — Luiggi Mendoza, Aug 29 '12 at 17:14
No Actually values and keys are coming from caouchdb, and i have to use this map to show on u.i. Where key is the label and value is the value next to label. — vikas27, Aug 29 '12 at 17:23
@vikasTheJavaDeveloper then you should follow the advice from Peter Lawrey: create a class that will have the attributes "name", "email", and others, then you fill it with the data and you can display it easily in your UI. — Luiggi Mendoza, Aug 29 '12 at 17:29
@Dan something I've learned here on SO is that OP won't (always) write the real problem, instead the problem with the solution he/she tries to apply :). — Luiggi Mendoza, Aug 29 '12 at 17:30

score 2 · Answer 1 · answered Aug 29 '12 at 17:14

2

HashMap is not a sorted or sortable collection.

What you can do is use TreeMap with your own Comparator.

However, I suspect you would be better off using a real class instead of an ad-hoc Map.

answered Aug 29 '12 at 17:14

Peter Lawrey

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I wouldn't suggest treemap for performance reason. For this case a linkedhashmap with custom compartor with be ok. – Nomad Sep 08 '12 at 19:12
LinkedHashMap doesn't take a custom comparator, or a custom hash function either. – Peter Lawrey Sep 09 '12 at 15:07

score 0 · Answer 2 · answered Aug 29 '12 at 17:13

0

Instead of using HashMap, you should use a LinkedHashMap because it preserves the order you add the elements. You would have to add the elements in the order you need them.

answered Aug 29 '12 at 17:13

Dan D.

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score 0 · Answer 3 · answered Aug 29 '12 at 17:14

0

You can use a tree map. The constructor accepts a comparator.

You can pass your own implementation of the comparator where in you can implement the logic of ordering the data in your map.

answered Aug 29 '12 at 17:14

Scorpion

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score 0 · Answer 4 · edited May 23 '17 at 11:49

I would suggest that you create a bean e.g. Contact or Person and then write comparator for this.

So once you are done creating bean and comparator for it. Then

Populate the list/collection of bean

and the finally do

Collection.sort(yourlist,sortByNameComparator);

Collection.sort(yourlist,sortByemailComparator);

Where sortByNameComparator and sortByemailComparator are the comparators you created.

Take a look at this. it will definitely solve your problem.

Sorting an ArrayList of Contacts based on name?

The above has example of creating comparators.

score -1 · Answer 5 · answered Aug 29 '12 at 17:17

-1

Depending on your usage, you might want to use a List<Pair>, where Pair is something like

public class Pair<J,K> {
    private J key;
    private K value;

    public Pair(J key, K value) {
        this.key = key;
        this.value = value;
    }

    public J getKey() {return key;}
    public K getValue() {return value;}
}

answered Aug 29 '12 at 17:17

Stuart

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How's this supposed to help OP in the current problem? Using this list will become useless if someone needs to use a fast and good `get` method. – Luiggi Mendoza Aug 29 '12 at 17:20

Sorting map according to user defined criteria?

5 Answers5