Добавил немного примеров со стримами

src/main/java/dev/struchkov/example/debugger/seven/Employee.java

@@ -0,0 +1,89 @@
+package dev.struchkov.example.debugger.seven;
+
+public class Employee {
+
+    private String firstName;
+    private String lastName;
+    private Integer age;
+    private Integer salary;
+    private Position position;
+
+    public Employee(String firstName, String lastName, Integer age, Integer salary, Position position) {
+        this.firstName = firstName;
+        this.lastName = lastName;
+        this.age = age;
+        this.salary = salary;
+        this.position = position;
+    }
+
+    public String getFirstName() {
+        return firstName;
+    }
+
+    public void setFirstName(String firstName) {
+        this.firstName = firstName;
+    }
+
+    public String getLastName() {
+        return lastName;
+    }
+
+    public void setLastName(String lastName) {
+        this.lastName = lastName;
+    }
+
+    public Integer getAge() {
+        return age;
+    }
+
+    public void setAge(Integer age) {
+        this.age = age;
+    }
+
+    public Position getPosition() {
+        return position;
+    }
+
+    public void setPosition(Position position) {
+        this.position = position;
+    }
+
+    public Integer getSalary() {
+        return salary;
+    }
+
+    public void setSalary(Integer salary) {
+        this.salary = salary;
+    }
+
+    @Override
+    public String toString() {
+        return position + " " + firstName + " " + lastName + " " + age + " лет, зарплата: " + salary;
+    }
+
+    public static Employee of(String firstName, String lastName, Integer age, Integer salary, Position position) {
+        return new Employee(firstName, lastName, age, salary, position);
+    }
+
+    public enum Position {
+        DEV("Разработчик"),
+        ACCOUNTANT("Бухгалтер"),
+        BOSS("Начальник отдела");
+
+        private final String title;
+
+        Position(String title) {
+            this.title = title;
+        }
+
+        public String getTitle() {
+            return title;
+        }
+
+        @Override
+        public String toString() {
+            return title;
+        }
+    }
+
+}

src/main/java/dev/struchkov/example/debugger/seven/StreamMain.java

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+package dev.struchkov.example.debugger.seven;
+
+import dev.struchkov.example.debugger.seven.Employee.Position;
+
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+import static dev.struchkov.example.debugger.seven.Employee.Position.ACCOUNTANT;
+import static dev.struchkov.example.debugger.seven.Employee.Position.BOSS;
+import static dev.struchkov.example.debugger.seven.Employee.Position.DEV;
+
+public class StreamMain {
+
+    public static void main(String[] args) {
+
+        final List<Employee> employees = List.of(
+                Employee.of("Екатерина", "Козлова", 28, 2_000_000, BOSS),
+                Employee.of("Алексей", "Кузнецов", 45, 90_000, ACCOUNTANT),
+                Employee.of("Юлия", "Козлова", 18, 35_000, ACCOUNTANT),
+                Employee.of("Никита", "Васильев", 22, 110_000, DEV),
+                Employee.of("Иван", "Иванов", 30, 300_000, DEV),
+                Employee.of("Анна", "Ермолова", 45, null, DEV),
+                Employee.of("Ирина", "Колесникова", 35, 200_000, DEV)
+        );
+
+        final Set<String> devs = employees.stream()
+                .filter(employee -> DEV.equals(employee.getPosition()))
+                .filter(employee -> employee.getSalary() != null)
+                .filter(employee -> employee.getSalary() > 150_000)
+                .map(Employee::getLastName)
+                .collect(Collectors.toSet());
+
+        final Map<Position, List<Employee>> collect = employees.stream()
+                .filter(employee -> employee.getSalary() != null)
+                .collect(Collectors.groupingBy(Employee::getPosition));
+
+    }
+
+}