Java + comparator + sorting

Question

I am getting Data from DB in the format List.

UserSession will have WorkStationName, UserName and AreaName.

Now I want to sort it first WorkStationname wise then userName and then AreaName.

How to do it in java? Is it possible to do it using Comparator?

I had created first area compersion then this list will again sort user comperision and then this list will again sort by Comparator of Workstation.But it did not give me the proper result.. — user223614, Oct 31 '13 at 13:19
Can't you use an ORDER BY clause in the database, assuming it is SQL? — EdgeCase, Oct 31 '13 at 14:34
Yes I can use it , But its a Criteria Query and data is not proper might be in Upper case or lower case , It will come in both the terms.So it does not produce the proper sorting result. — user223614, Nov 01 '13 at 09:38

score 1 · Answer 1 · answered Oct 31 '13 at 13:08

Best way:

public void sortAccordingToAboveRequirement(List<UserSession> userSessions){

 Collections.sort(userSessions,myComparator);

 }


  static Comparator<UserSession> myComparator=new Comparator<UserSession>() {
    @Override
        public int compare(UserSession user1, UserSession user2) {
        int value=0;
        value=user1.getWorkStationName().compareTo(user2.getWorkStationName())
        if(value!=0) return value;
        value=user1.getUserName().compareTo(user2.getUserName());
        if(value!=0) return value;
        value=user1.getAreaName().compareTo(user2.getAreaName());
        return value;
    }
};

Use compareToIgnoreCase() if you wish :)

score 0 · Answer 2 · edited May 23 '17 at 12:13

0

You can use a query to do it.
Or You can override a compare function.
This Post on stackoverflow will help you do that

edited May 23 '17 at 12:13

Community

1
1

answered Oct 31 '13 at 13:06

pratim_b

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It should rather be a comment, than the answer... – Eel Lee Oct 31 '13 at 13:09
yaah,I tried. but it says i need some reputation or points (whatever it is) to put it in a comment. Anyways a solution is always a solution. (I mean I tried to give). And see the upvoted answer. It is almost the same post link i gave – pratim_b Oct 31 '13 at 13:11
Try the answer given by me :) – Shoaib Chikate Oct 31 '13 at 13:13

score 0 · Answer 3 · answered Oct 31 '13 at 13:10

You can use a comparator or you can implement the compareable interface to you class. I give you an example for the secound way:

Collections.sort(UserSessionList);

The class UserSession must implements Comparable<UserSession> now. And then you can override the compareTo method of this class. For example:

@Override
public int compareTo(UserSession o) {

    if(null== o)
        return 1;
    if(getWorkStationName() == null && o.getWorkStationName()==null)
        return 0;
    if(getWorkStationName() == null && o.getWorkStationName()!=null)
        return -1;
    if(getWorkStationName() != null && o.getWorkStationName()==null)
        return 1;
    return o.getWorkStationName().compareTo(getWorkStationName());
}

The rest of the compare function you have to write by your own now! :)

Java + comparator + sorting

3 Answers3