Sorting specific object of ArrayList

Question

I have the following ArrayList hashmap:

 [{username=p, diff=0.0}, {username=e , diff=314.0}, {username=e ,diff=90.0}, {username=p, diff=0.0}, {username=e, diff=94.0}, {username=z, diff=92.0} , {username=z, diff=102.0}  ]

Implementing code below i get the whole list sorted by "diff" key:

Collections.sort(final_itinList,
                            new Comparator<HashMap<String, String>>() {

                                @Override
                                public int compare(HashMap<String, String> lhs,
                                        HashMap<String, String> rhs) {                                  

                                    return Double.compare(
                                            Double.parseDouble(lhs.get("diff")),
                                            Double.parseDouble(rhs.get("diff")));

                                }
                            });

Now i have difficulties to sort the list by "diff" key only for these objects that have username different as "p". So I want for objects that have "p" username to stay at their positions and sort the others,like...

[{username=p, diff=0.0}, {username=e ,diff=90.0}, {username=e , diff=314.0},  {username=p, diff=0.0}, {username=z, diff=92.0} , {username=e, diff=94.0}, {username=z, diff=102.0}  ]

Any quick solution; Thanks in advance

eracube · Accepted Answer · 2015-01-24 14:36:11Z

1

If I understand well your problem, the quick solution will be to do like follows:

Collections.sort(final_itinList,
                        new Comparator<HashMap<String, String>>() {

                            @Override
                            public int compare(HashMap<String, String> lhs,
                                    HashMap<String, String> rhs) {                                  

                                    if( (lhs.get("username").compareTo("p")) == 0){
                                      return -1;
                                    }
                                return Double.compare(
                                        Double.parseDouble(lhs.get("diff")),
                                        Double.parseDouble(rhs.get("diff")));

                            }
                        });

This will check the username and if it is "p" then its value will be returned and its position will be the same as before!

edited Jan 24, 2015 at 14:36

answered Jan 24, 2015 at 13:51

eracube

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2 Comments

Fenia Kechagia Over a year ago

I get "Type mismatch: cannot convert from String to int" at line " return (lhs.get("diff"));"

eracube Over a year ago

I have edited my answer! Hope this will work. Otherwise you have to return positive value instead ! If you want to sort by descending order you have to return 1 otherwise return negative value!

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