Solution for Stream API 02

Exercise.java

@@ -1,6 +1,8 @@
 public class Exercise {
 
   public static void main(String[] args) {
-    // implement exercise here
+    Queries queries = new Queries(DataProvider.getFootballers());
+    queries.getAllFootballersByBirthyear().values().stream().forEach(System.out::println);
+    // add more queries as you wish
   }
 }

FootballClub.java

@@ -0,0 +1 @@
+public record FootballClub(String name, int positionInAllTimeTable, int pointsInAllTimeTable) {}

Footballer.java

@@ -0,0 +1,10 @@
+import java.time.LocalDate;
+
+public record Footballer(
+    String name,
+    Position position,
+    LocalDate birthDate,
+    int sizeInCm,
+    FootballClub footballClub,
+    int numberOfGames,
+    int numberOfGoals) {}

Position.java

@@ -0,0 +1,6 @@
+public enum Position {
+  GOALKEEPER,
+  DEFENDER,
+  MIDFIELDER,
+  STRIKER;
+}

Queries.java

@@ -0,0 +1,58 @@
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.OptionalDouble;
+import java.util.function.Function;
+import java.util.function.Predicate;
+import java.util.stream.Collectors;
+
+public class Queries {
+
+  private ArrayList<Footballer> footballers;
+
+  public Queries(ArrayList<Footballer> footballers) {
+    this.footballers = footballers;
+  }
+
+  public int getTotalOfAllGoalsByMidfielders() {
+    return footballers.stream()
+        .filter(footballer -> footballer.position().equals(Position.MIDFIELDER))
+        .mapToInt(footballer -> footballer.numberOfGoals())
+        .sum();
+  }
+
+  public Optional<Footballer> getNameOfVfLWolfsburgFootballerWithMostPlayedGames() {
+    Predicate<Footballer> isFromWolfsburg =
+        footballer -> footballer.footballClub().equals(new FootballClub("VfL Wolfsburg", 3, 1145));
+    Comparator<Footballer> sortNumberOfGoalsAscending =
+        (footballer1, footballer2) ->
+            Integer.valueOf(footballer1.numberOfGames()).compareTo(footballer2.numberOfGames());
+
+    return footballers.stream().filter(isFromWolfsburg).max(sortNumberOfGoalsAscending);
+  }
+
+  public List<FootballClub> getNameOfAllFootballClubs() {
+    return footballers.stream().map(footballer -> footballer.footballClub()).distinct().toList();
+  }
+
+  public boolean isFootballerWithSizeInCmLT170AndNumbreOfGoalsBT0() {
+    return footballers.stream()
+        .anyMatch(footballer -> footballer.sizeInCm() < 170 && footballer.numberOfGoals() > 0);
+  }
+
+  public Map<Integer, List<Footballer>> getAllFootballersByBirthyear() {
+    Function<Footballer, Integer> birthYear = footballer -> footballer.birthDate().getYear();
+    return footballers.stream().collect(Collectors.groupingBy(birthYear));
+  }
+
+  public OptionalDouble getAverageNumberOfPointsFromAllBundesligaFootballClubs() {
+    return footballers.stream()
+        .map(footballer -> footballer.footballClub())
+        .distinct()
+        .filter(footballClub -> footballClub.positionInAllTimeTable() != -1)
+        .mapToInt(footballClub -> footballClub.pointsInAllTimeTable())
+        .average();
+  }
+}