Examples of comparator in Java

Business requirements:

Descending by number of participants, then by rank and ascending

Number of people: pertotal, ranking of the sum: ranktotal

Full code:

@Overridepublic jsonobject gettopunitofgameranking (list<map<long, integer>> usermap,int limit) { Jsonobject json = new Jsonobject (); list<jsonobject> list = new arraylist<jsonobject> (); list<jsonobject> lists = new arraylist<jsonobject> (); list<long> userids = new arraylist<long> (); for (Map<long, integer> Userranking:usermap) {for (Long UserId:userRanking.keySet ()) {Userids.add (userId);}} if (userids! = null && userids.size () > 0) {list<object> param = new arraylist<object> (); StringBuilder builder = new StringBuilder (); Builder.append ("Select Unit_id,count (user_id) as Pertotal from T_user_ Expand where unit_id!=0 and user_id in ("), for (int i = 0; I < userids.size (); i++) {if (I! = 0) {builder.append (",");} Builder.append ("?"); Param.add (Userids.get (i)); Builder.append (") GROUP by unit_id ORDER BY pertotal desc limit?"); Param.add (limit);//final list<long> unitids = new arraylist<long> (); List = prImaryjdbctemplate.query (Builder.tostring (), Param.toarray (), new rowmapper<jsonobject> () {@Overridepublic Jsonobject Maprow (ResultSet rs, int rowNum) throws SQLException {jsonobject o = new Jsonobject (); O.put ("Unitid", Rs.getlon G ("unit_id")); O.put ("Pertotal", Rs.getlong ("Pertotal")); return o;}); list<object> params = new arraylist<object> (); StringBuilder builders = new StringBuilder (); Builders.append ("Select unit_id,user_id from T_user_expand where unit_id! = 0 and user_id in ("), for (int i = 0; I < userids.size (); i++) {if (I! = 0) {builders.append (",");} Builders.append ("?"); Params.add (Userids.get (i)); Builders.append (") limit?"); Params.add (limit); lists = Primaryjdbctemplate.query (Builders.tostring (), Params.toarray (), New rowmapper< Jsonobject> () {@Overridepublic jsonobject Maprow (ResultSet rs, int rowNum) throws SQLException {jsonobject o = new JSON Object (); O.put ("Unitid", Rs.getlong ("unit_id")), O.put ("user_id", Rs.getlong ("user_id")); return o;}); for (JSONobject obj:lists) {//traverse "User ID" associated "Province ID" for (map<long, integer> user:usermap) {///by "User ID" to get the corresponding ranking Integer rank =user . Get (Obj.get ("user_id")); if (null = = rank) {rank = 0;} for (Jsonobject object:list) {if ((long) object.get ("Unitid"). CompareTo ((Long) obj.get ("Unitid")) {Integer Oldranktotal = (Integer) object.get ("Ranktotal"); if (null = = Oldranktotal) {oldranktotal = 0;} Object.put ("Ranktotal", Oldranktotal + Rank);}}}} Collections.sort (list, new comparator<jsonobject> () {/** *) first descending by number of participants and then ascending by rank */@Overridepublic int Compare ( Jsonobject O1, Jsonobject O2) {Long perTotal1 = (long) o1.get ("Pertotal"); Long PerTotal2 = (long) o2.get ("Pertotal"), Integer rankTotal1 = (integer) o1.get ("Ranktotal"), Integer rankTotal2 = ( Integer) o2.get ("Ranktotal"); if (Pertotal1.compareto (PerTotal2) > 0) {return-1;} else if (Pertotal1.compareto (PerTotal2) < 0) {return 1;} Else{if (Ranktotal1.compareto (RankTotal2) > 0) {return 1;} else if (Ranktotal1.compareto (RankTotal2) < 0) {return-1;} Else{return 0;}}});Json.put ("Data", list); return JSON;} 

key part code (in the same number of cases, compare the sum of the rankings):

list<jsonobject> list = new arraylist<jsonobject> (); Collections.sort (list, new comparator<jsonobject> () {/** *) first descending by number of participants and then ascending by rank */@Overridepublic int Compare ( Jsonobject O1, Jsonobject O2) {Long perTotal1 = (long) o1.get ("Pertotal"); Long PerTotal2 = (long) o2.get ("Pertotal"), Integer rankTotal1 = (integer) o1.get ("Ranktotal"), Integer rankTotal2 = ( Integer) o2.get ("Ranktotal"); if (Pertotal1.compareto (PerTotal2) > 0) {return-1;} else if (Pertotal1.compareto (PerTotal2) < 0) {return 1;} Else{if (Ranktotal1.compareto (RankTotal2) > 0) {return 1;} else if (Ranktotal1.compareto (RankTotal2) < 0) {return-1;} Else{return 0;}}});

Examples of comparator in Java