java - Java8 Collecting data from 2 different object streams to a sorted list of 3rd object -

so here's problem. have 3 classes below:

class objectclassa {     private final long id;     private final string name;     private final boolean isreadonly;     //<some more fields>      long getid()     {         return this.id;     }      string getname()     {         return this.name;     }      boolean isreadonly()     {         return this.isreadonly;     } }  class objectclassb {     private final long id;     private final string location;     private final boolean isreadonly;     //<some more fields>      long getid()     {         return this.id;     }      string getlocation()     {         return this.location;     }      boolean isreadonly()     {         return this.isreadonly;     } } 

and

class objectclassc {     private final string location;     private final boolean isreadonly;     private final string location;      string getname()     {         return this.name;     }      boolean isreadonly()     {         return this.isreadonly;     }      string getlocation()     {         return this.location;     } } 

i have 2 maps -

map<id,objectclassa> mapobjectclassa  

and

map<id,objectclassb> mapobjectclassb 

both these maps of same size. id keys common both maps. aim iterate on either maps create sorted (by objectclassc.name) list<objectclassc> objects such that:

objectclassc.name = objectclassa.name objectclassc.isreadonly = objectclassa.isreadonly || objectclassb.isreadonly objectclassc.location = objectclassb.location 

this logic have right follows:

final list<objectclassc> list =  mapobjectclassa.values()                .stream()                .map(a -> {                     new objectclassc(a.getname(),                                      a.isreadonly() || mapobjectclassb.get(a.getid).isreadonly(),                                      mapobjectclassb.get(a.getid).getlocation())                 })                .sorted(comparator.comparing(objectclassc::getname))                .collect(collectors.<objectclassc> tolist()); 

my mapping , collection working fine, don't sorted collection of objectclassc objects. please point out i'm going wrong?

not nice, works.

public class mapmerge_38837365 {      public static void main(string[] args) {         map<integer, a> = new hashmap();         as.put(1, new a("anna"));         as.put(2, new a("maria"));         as.put(3, new a("eva"));          map<integer, b> bs = new hashmap();         bs.put(1, new b("adam"));         bs.put(2, new b("edward"));         bs.put(3, new b("jon"));          stream.concat(                 as.entryset().stream(),                 bs.entryset().stream()         ).collect(collectors.groupingby(map.entry::getkey))                 .entryset().stream()                 .map(e -> e.getvalue())                 .map(e -> {                     if (e.get(0).getvalue() instanceof a)                         return new ab((a) e.get(0).getvalue(), (b) e.get(1).getvalue());                     return new ab((a) e.get(1).getvalue(), (b) e.get(0).getvalue());                 })                 .map(ab -> new c(ab.a.name+" " +ab.b.name))                 .foreach(system.out::println);     } } 

"the high magic" happens in stream.concat groupingby. in 2 lines create stream of entries both maps. group them key map. elements same key (id) go 1 list<object>. next step create new stream grouping map entryset().stream().

then extract value - entries same id > map(e -> e.getvalue()).

next step build ab objects , omitted want extract type check , cast function. have pseudo pair ab, nice candidate create c class map(ab -> new c(ab.a.name+" " +ab.b.name)).

classes a, b, c , ab:

class {      final string name;      a(string name) {         this.name = name;     }      @override     public string tostring() {         return "a{" +                 "name='" + name + '\'' +                 '}';     } }  class b {      final string name;      b(string name) {         this.name = name;     }      @override     public string tostring() {         return "b{" +                 "name='" + name + '\'' +                 '}';     } }  class c {      final string name;      c(string name) {         this.name = name;     }      @override     public string tostring() {         return "c{" +                 "name='" + name + '\'' +                 '}';     } }  class ab {      final a;     final b b;      ab(a a, b b) {         this.a = a;         this.b = b;     }      @override     public string tostring() {         return "ab{" +                 "a=" + +                 ", b=" + b +                 '}';     } }