2323
2424package com .iluwatar .collectionpipeline ;
2525
26- import java .util .Collection ;
26+ import java .util .ArrayList ;
2727import java .util .Collections ;
2828import java .util .Comparator ;
29+ import java .util .HashMap ;
2930import java .util .List ;
3031import java .util .Map ;
31- import java .util .stream .Collectors ;
3232
3333/**
3434 * Imperative-style programming to iterate over the list and get the names of cars made later than
@@ -57,11 +57,27 @@ private ImperativeProgramming() {
5757 * @return {@link List} of {@link String} of car models built after year 2000
5858 */
5959public static List <String >getModelsAfter2000 (List <Car >cars ) {
60- return cars .stream ()
61- .filter (car ->car .getYear () >2000 )
62- .sorted (Comparator .comparingInt (Car ::getYear ))
63- .map (Car ::getModel )
64- .collect (Collectors .toList ());
60+ List <Car >carsSortedByYear =new ArrayList <>();
61+
62+ for (Car car :cars ) {
63+ if (car .getYear () >2000 ) {
64+ carsSortedByYear .add (car );
65+ }
66+ }
67+
68+ Collections .sort (carsSortedByYear ,new Comparator <Car >() {
69+ @ Override
70+ public int compare (Car car1 ,Car car2 ) {
71+ return car1 .getYear () -car2 .getYear ();
72+ }
73+ });
74+
75+ List <String >models =new ArrayList <>();
76+ for (Car car :carsSortedByYear ) {
77+ models .add (car .getModel ());
78+ }
79+
80+ return models ;
6581 }
6682
6783/**
@@ -71,7 +87,17 @@ public static List<String> getModelsAfter2000(List<Car> cars) {
7187 * @return {@link Map} with category as key and cars belonging to that category as value
7288 */
7389public static Map <Category ,List <Car >>getGroupingOfCarsByCategory (List <Car >cars ) {
74- return cars .stream ().collect (Collectors .groupingBy (Car ::getCategory ));
90+ Map <Category ,List <Car >>groupingByCategory =new HashMap <>();
91+ for (Car car :cars ) {
92+ if (groupingByCategory .containsKey (car .getCategory ())) {
93+ groupingByCategory .get (car .getCategory ()).add (car );
94+ }else {
95+ List <Car >categoryCars =new ArrayList <>();
96+ categoryCars .add (car );
97+ groupingByCategory .put (car .getCategory (),categoryCars );
98+ }
99+ }
100+ return groupingByCategory ;
75101 }
76102
77103/**
@@ -82,11 +108,25 @@ public static Map<Category, List<Car>> getGroupingOfCarsByCategory(List<Car> car
82108 * @return {@link List} of {@link Car} to belonging to the group
83109 */
84110public static List <Car >getSedanCarsOwnedSortedByDate (List <Person >persons ) {
85- return persons .stream ()
86- .map (Person ::getCars )
87- .flatMap (Collection ::stream )
88- .filter (car ->car .getCategory () ==Category .SEDAN )
89- .sorted (Comparator .comparingInt (Car ::getYear ))
90- .collect (Collectors .toList ());
111+ List <Car >cars =new ArrayList <>();
112+ for (Person person :persons ) {
113+ cars .addAll (person .getCars ());
114+ }
115+
116+ List <Car >sedanCars =new ArrayList <>();
117+ for (Car car :cars ) {
118+ if (Category .SEDAN .equals (car .getCategory ())) {
119+ sedanCars .add (car );
120+ }
121+ }
122+
123+ sedanCars .sort (new Comparator <Car >() {
124+ @ Override
125+ public int compare (Car o1 ,Car o2 ) {
126+ return o1 .getYear () -o2 .getYear ();
127+ }
128+ });
129+
130+ return sedanCars ;
91131 }
92132}