docs: Collection pipeline explanation (#2875)

* collection pipeline docs + refactoring

* restore imperative programming code

collection-pipeline/src/main/java/com/iluwatar/collectionpipeline/Car.java

@@ -22,22 +22,11 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
-package com.iluwatar.collectionpipeline;
 
-import lombok.EqualsAndHashCode;
-import lombok.Getter;
-import lombok.RequiredArgsConstructor;
+package com.iluwatar.collectionpipeline;
 
 /**
  * A Car class that has the properties of make, model, year and category.
  */
-@Getter
-@EqualsAndHashCode
-@RequiredArgsConstructor
-public class Car {
-  private final String make;
-  private final String model;
-  private final int year;
-  private final Category category;
-
-}
+public record Car(String make, String model, int year, Category category) {
+}

collection-pipeline/src/main/java/com/iluwatar/collectionpipeline/FunctionalProgramming.java

@@ -22,6 +22,7 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
+
 package com.iluwatar.collectionpipeline;
 
 import java.util.Comparator;
@@ -54,9 +55,8 @@ public class FunctionalProgramming {
    * @return {@link List} of {@link String} representing models built after year 2000
    */
   public static List<String> getModelsAfter2000(List<Car> cars) {
-    return cars.stream().filter(car -> car.getYear() > 2000)
-        .sorted(Comparator.comparing(Car::getYear))
-        .map(Car::getModel).toList();
+    return cars.stream().filter(car -> car.year() > 2000).sorted(Comparator.comparing(Car::year))
+        .map(Car::model).toList();
   }
 
   /**
@@ -66,7 +66,7 @@ public class FunctionalProgramming {
    * @return {@link Map} with category as key and cars belonging to that category as value
    */
   public static Map<Category, List<Car>> getGroupingOfCarsByCategory(List<Car> cars) {
-    return cars.stream().collect(Collectors.groupingBy(Car::getCategory));
+    return cars.stream().collect(Collectors.groupingBy(Car::category));
   }
 
   /**
@@ -76,8 +76,8 @@ public class FunctionalProgramming {
    * @return {@link List} of {@link Car} to belonging to the group
    */
   public static List<Car> getSedanCarsOwnedSortedByDate(List<Person> persons) {
-    return persons.stream().map(Person::getCars).flatMap(List::stream)
-        .filter(car -> Category.SEDAN.equals(car.getCategory()))
-        .sorted(Comparator.comparing(Car::getYear)).toList();
+    return persons.stream().map(Person::cars).flatMap(List::stream)
+        .filter(car -> Category.SEDAN.equals(car.category()))
+        .sorted(Comparator.comparing(Car::year)).toList();
   }
 }

collection-pipeline/src/main/java/com/iluwatar/collectionpipeline/ImperativeProgramming.java

@@ -61,7 +61,7 @@ public class ImperativeProgramming {
     List<Car> carsSortedByYear = new ArrayList<>();
 
     for (Car car : cars) {
-      if (car.getYear() > 2000) {
+      if (car.year() > 2000) {
         carsSortedByYear.add(car);
       }
     }
@@ -69,13 +69,13 @@ public class ImperativeProgramming {
     Collections.sort(carsSortedByYear, new Comparator<Car>() {
       @Override
       public int compare(Car car1, Car car2) {
-        return car1.getYear() - car2.getYear();
+        return car1.year() - car2.year();
       }
     });
 
     List<String> models = new ArrayList<>();
     for (Car car : carsSortedByYear) {
-      models.add(car.getModel());
+      models.add(car.model());
     }
 
     return models;
@@ -90,12 +90,12 @@ public class ImperativeProgramming {
   public static Map<Category, List<Car>> getGroupingOfCarsByCategory(List<Car> cars) {
     Map<Category, List<Car>> groupingByCategory = new HashMap<>();
     for (Car car : cars) {
-      if (groupingByCategory.containsKey(car.getCategory())) {
-        groupingByCategory.get(car.getCategory()).add(car);
+      if (groupingByCategory.containsKey(car.category())) {
+        groupingByCategory.get(car.category()).add(car);
       } else {
         List<Car> categoryCars = new ArrayList<>();
         categoryCars.add(car);
-        groupingByCategory.put(car.getCategory(), categoryCars);
+        groupingByCategory.put(car.category(), categoryCars);
       }
     }
     return groupingByCategory;
@@ -111,12 +111,12 @@ public class ImperativeProgramming {
   public static List<Car> getSedanCarsOwnedSortedByDate(List<Person> persons) {
     List<Car> cars = new ArrayList<>();
     for (Person person : persons) {
-      cars.addAll(person.getCars());
+      cars.addAll(person.cars());
     }
 
     List<Car> sedanCars = new ArrayList<>();
     for (Car car : cars) {
-      if (Category.SEDAN.equals(car.getCategory())) {
+      if (Category.SEDAN.equals(car.category())) {
         sedanCars.add(car);
       }
     }
@@ -124,7 +124,7 @@ public class ImperativeProgramming {
     sedanCars.sort(new Comparator<Car>() {
       @Override
       public int compare(Car o1, Car o2) {
-        return o1.getYear() - o2.getYear();
+        return o1.year() - o2.year();
       }
     });
 

collection-pipeline/src/main/java/com/iluwatar/collectionpipeline/Person.java

@@ -25,16 +25,8 @@
 package com.iluwatar.collectionpipeline;
 
 import java.util.List;
-import lombok.Getter;
-import lombok.RequiredArgsConstructor;
 
 /**
  * A Person class that has the list of cars that the person owns and use.
  */
-@Getter
-@RequiredArgsConstructor
-public class Person {
-
-  private final List<Car> cars;
-
-}
+public record Person(List<Car> cars) {}