How to remove item from list based on attribute comparison?

Question

I have a list of objects "Artical" which have 2 attributes articalid and articalVersion as shown below.

enter public class Artical{
public int articalid;
public double articalVersion;
//with getter and setters
}

and now have list having following result

articalid=1098  articalVersion=1.0
articalid=1098  articalVersion=1.1
articalid=1078  articalVersion=1.0
articalid=1078  articalVersion=1.1
articalid=1065  articalVersion=1.0
articalid=1043  articalVersion=1.0

now I want to make list that contain only that objects that have greater version no.(and articalid must not repeat ) like

articalid=1098  articalVersion=1.1
articalid=1078  articalVersion=1.1
articalid=1065  articalVersion=1.0
articalid=1043  articalVersion=1.0

Answer 1

First you sort your List

Collections.sort(articleList, new ArticalComparatorSort());

By using the following comparator:

class ArticalComparatorSort implements Comparator<Artical>
{

    @Override
    public int compare(Artical a1, Artical a2)
    {
        if(a1.getArticalid() < a2.getArticalid()){
            return -1;
        }
        else if(a1.getArticalid() > a2.getArticalid()){
            return  1;
        }
        else{ // When both id are equals
            return Double.compare(a2.getArticalVersion(), a1.getArticalVersion());
        }
    }

}

This will sort as:

[1043 : 1.0
, 1065 : 1.0
, 1078 : 1.1
, 1078 : 1.0
, 1098 : 1.1
, 1098 : 1.0

Then use a TreeSet to remove duplicates

Set<Artical> mySet = new TreeSet<Artical>(new ArticalComparatorSet());

For TreeSet use the following comperator:

class ArticalComparatorSet implements Comparator<Artical>
{

    @Override
    public int compare(Artical a1, Artical a2)
    {
        if(a1.getArticalid() < a2.getArticalid()){
            return -1;
        }
        else if(a1.getArticalid() > a2.getArticalid()){
            return  1;
        }
        else{ 
            return 0;
        }
    }

}

This will remove duplicates as:

[1043 : 1.0
, 1065 : 1.0
, 1078 : 1.1
, 1098 : 1.1 

So you need to add only these three lines of code for removing duplicates:

Collections.sort(articleList, new ArticalComparatorSort());

Set<Artical> mySet = new TreeSet<Artical>(new ArticalComparatorSet());

mySet.addAll(articleList);

And only implement the above comparators

Answer 2

Do like this over an iteration

         Map<Integer,Artical> outPuts = new HashMap<Integer,Artical>();
 for(Artical artical1 : articals ){
     for(Artical artical2 : articals ){
             if(artical1.getarticalid() == artical2.getarticalid()){
             int retval = Double.compare(artical1.getarticalVersion(), artical2.getarticalVersion());
             if(retval > 0) {
                 if(outPuts.containsKey(artical1.getarticalid())){
                     outPuts.remove(artical1.getarticalid());
                     outPuts.add(artical1.getarticalid(),artical1);
                 }else{
                     outPuts.add(artical1.getarticalid(),artical1);
                 }
                 }
             else{
                 if(outPuts.containsKey(artical1.getarticalid())){
                     outPuts.remove(artical1.getarticalid());
                     outPuts.add(artical1.getarticalid(),artical1);
                 }else{
                     outPuts.add(artical1.getarticalid(),artical1);
                 }
                 }
         }
     }
 }