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Fix imperative-style. (#1180)

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Signed-off-by: yichen88 <tang.yichenyves@gmail.com>
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yichen88 2020-03-07 12:12:06 +01:00 committed by GitHub
parent 33682ad3e8
commit 33e4a870ca
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1 changed files with 54 additions and 14 deletions
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68
collection-pipeline/src/main/java/com/iluwatar/collectionpipeline/ImperativeProgramming.java
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@ -23,12 +23,12 @@
package com.iluwatar.collectionpipeline; package com.iluwatar.collectionpipeline;
import java.util.Collection; import java.util.ArrayList;
import java.util.Collections; import java.util.Collections;
import java.util.Comparator; import java.util.Comparator;
import java.util.HashMap;
import java.util.List; import java.util.List;
import java.util.Map; import java.util.Map;
import java.util.stream.Collectors;
/** /**
* Imperative-style programming to iterate over the list and get the names of cars made later than * Imperative-style programming to iterate over the list and get the names of cars made later than
@ -57,11 +57,27 @@ public class ImperativeProgramming {
* @return {@link List} of {@link String} of car models built after year 2000 * @return {@link List} of {@link String} of car models built after year 2000
*/ */
public static List<String> getModelsAfter2000(List<Car> cars) { public static List<String> getModelsAfter2000(List<Car> cars) {
return cars.stream() List<Car> carsSortedByYear = new ArrayList<>();
.filter(car -> car.getYear() > 2000)
.sorted(Comparator.comparingInt(Car::getYear)) for (Car car : cars) {
.map(Car::getModel) if (car.getYear() > 2000) {
.collect(Collectors.toList()); carsSortedByYear.add(car);
}
}
Collections.sort(carsSortedByYear, new Comparator<Car>() {
@Override
public int compare(Car car1, Car car2) {
return car1.getYear() - car2.getYear();
}
});
List<String> models = new ArrayList<>();
for (Car car : carsSortedByYear) {
models.add(car.getModel());
}
return models;
} }
/** /**
@ -71,7 +87,17 @@ public class ImperativeProgramming {
* @return {@link Map} with category as key and cars belonging to that category as value * @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) { public static Map<Category, List<Car>> getGroupingOfCarsByCategory(List<Car> cars) {
return cars.stream().collect(Collectors.groupingBy(Car::getCategory)); Map<Category, List<Car>> groupingByCategory = new HashMap<>();
for (Car car : cars) {
if (groupingByCategory.containsKey(car.getCategory())) {
groupingByCategory.get(car.getCategory()).add(car);
} else {
List<Car> categoryCars = new ArrayList<>();
categoryCars.add(car);
groupingByCategory.put(car.getCategory(), categoryCars);
}
}
return groupingByCategory;
} }
/** /**
@ -82,11 +108,25 @@ public class ImperativeProgramming {
* @return {@link List} of {@link Car} to belonging to the group * @return {@link List} of {@link Car} to belonging to the group
*/ */
public static List<Car> getSedanCarsOwnedSortedByDate(List<Person> persons) { public static List<Car> getSedanCarsOwnedSortedByDate(List<Person> persons) {
return persons.stream() List<Car> cars = new ArrayList<>();
.map(Person::getCars) for (Person person : persons) {
.flatMap(Collection::stream) cars.addAll(person.getCars());
.filter(car -> car.getCategory() == Category.SEDAN) }
.sorted(Comparator.comparingInt(Car::getYear))
.collect(Collectors.toList()); List<Car> sedanCars = new ArrayList<>();
for (Car car : cars) {
if (Category.SEDAN.equals(car.getCategory())) {
sedanCars.add(car);
}
}
sedanCars.sort(new Comparator<Car>() {
@Override
public int compare(Car o1, Car o2) {
return o1.getYear() - o2.getYear();
}
});
return sedanCars;
} }
} }