Managing User Data: Filtering and Aggregation in Java

import java.util.HashMap;
import java.util.Map;

public class UserManager {
    private Map<String, UserProfile> users;

    public UserManager() {
        users = new HashMap<>();
    }

    public boolean addUser(String userId, int age, String country, boolean subscribed) {
        if (users.containsKey(userId)) {
            return false;
        }
        users.put(userId, new UserProfile(age, country, subscribed));
        return true;
    }

    public UserProfile getUser(String userId) {
        return users.get(userId);
    }

    public boolean updateUser(String userId, Integer age, String country, Boolean subscribed) {
        UserProfile profile = users.get(userId);
        if (profile == null) {
            return false;
        }
        if (age != null) {
            profile.setAge(age);
        }
        if (country != null) {
            profile.setCountry(country);
        }
        if (subscribed != null) {
            profile.setSubscribed(subscribed);
        }
        return true;
    }
}

class UserProfile {
    private int age;
    private String country;
    private boolean subscribed;

    public UserProfile(int age, String country, boolean subscribed) {
        this.age = age;
        this.country = country;
        this.subscribed = subscribed;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getCountry() {
        return country;
    }

    public void setCountry(String country) {
        this.country = country;
    }

    public boolean isSubscribed() {
        return subscribed;
    }

    public void setSubscribed(boolean subscribed) {
        this.subscribed = subscribed;
    }

    @Override
    public String toString() {
        return "UserProfile{" + "age=" + age + ", country='" + country + '\'' + ", subscribed=" + subscribed + '}';
    }
}

class Program {
    public static void main(String[] args) {
        UserManager um = new UserManager();
        System.out.println(um.addUser("u1", 25, "USA", true));  // true, Adds new user
        System.out.println(um.addUser("u2", 30, "Canada", false));  // true, Adds another user
        System.out.println(um.addUser("u1", 22, "Mexico", true));  // false, User exists
        System.out.println(um.getUser("u1"));  // UserProfile with specified attributes
        System.out.println(um.updateUser("u1", 26, null, null));  // true, Only updates age
        System.out.println(um.updateUser("u3", 19, "UK", false));  // false, User does not exist
        System.out.println(um.updateUser("u1", null, "UK", true)); // true, Updates country and subscription status
    }
}