import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class StreamExample {
    public static void main(String[] args) {
        List<String> names = Arrays.asList("Alice", "Bob", "Charlie", "David");

        List<String> filteredNames = names.stream()
            .filter(name -> name.length() > 4)
            .map(String::toUpperCase)
            .collect(Collectors.toList());

        System.out.println(filteredNames); // [ALICE, CHARLIE, DAVID]
    }
}

import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public class AdvancedStreams {
    public static void main(String[] args) {
        List<Person> people = Arrays.asList(
            new Person("John", 25, "Developer"),
            new Person("Jane", 30, "Designer"),
            new Person("Bob", 25, "Developer")
        );

        // Group by profession and count
        Map<String, Long> professionCount = people.stream()
            .collect(Collectors.groupingBy(
                Person::getProfession,
                Collectors.counting()
            ));

        // Find average age by profession
        Map<String, Double> avgAgeByProfession = people.stream()
            .collect(Collectors.groupingBy(
                Person::getProfession,
                Collectors.averagingInt(Person::getAge)
            ));
    }
}