More complex lambda examples

App.java

import java.util.*;
import java.util.function.Predicate;

/**
 * Created by iliesa on 22.09.2016.
 */
public class App {
    private ArrayList<User> users;

    public App() {
        users = new ArrayList<User>();
        setMockData();

        // listAllPersonsUsingLambda();
        // printUsersWithAnInstatiatedPredicate();
        // printUsersUsingLambdasDirectlyForFilteringTheSpanishOnes();
        // printUsersUsingLambdasDirectlyForFilteringTheSpanishOnesThatHaveAgeAboveFive();
        // printOlderUser();
    }

    private void setMockData() {
        ArrayList<String> contryArray = new ArrayList(Arrays.asList(Country.ITALY, Country.SPAIN, Country.IRELAND));
        for (int i = 0; i < 20; i++) {
            User user = new User("user" + i, i, contryArray.get(new Random().nextInt(3)));
            users.add(user);
        }
    }

    List<User> filterUsersByAge(List<User> users, UserPredicat p) {
        List<User> result = new ArrayList<>();
        for (User user : users) {
            if (p.testAge(user.getAge())) {
                result.add(user);
            }
        }
        return result;
    }

    private void listAllPersonsUsingLambda() {
        this.users.forEach(person -> {
            System.out.println(person.getCountry());
        });
    }

    private void printUsersWithAnInstatiatedPredicate() {
        Predicate italy = p -> {
            return Country.ITALY.equals(((User) p).getCountry());
        };

        this.users.stream().filter(italy).forEach((person) -> {
            System.out.println(((User) person).getCountry());
        });
    }

    private void printUsersUsingLambdasDirectlyForFilteringTheSpanishOnes() {
        this.users.stream().filter(person -> {
            return Country.SPAIN.equals(person.getCountry());
        }).forEach((eachPerson) -> {
            System.out.println(eachPerson.getCountry());
        });
    }

    private void printUsersUsingLambdasDirectlyForFilteringTheSpanishOnesThatHaveAgeAboveFive() {
        this.users.stream().filter(person -> {
            return Country.SPAIN.equals(person.getCountry()) && person.getAge() > 5;
        }).forEach((eachPerson) -> {
            System.out.println("Age: " + eachPerson.getAge() + "Country: " + eachPerson.getCountry());
        });
    }

    private void printUsersCountUsingLambdasDirectlyForFilteringTheSpanishOnesThatHaveAgeAboveFive() {
        this.users.stream().filter(person -> {
            return Country.SPAIN.equals(person.getCountry()) && person.getAge() > 5;
        }).count();
    }

    public void printOlderUser() {
        Predicate italy = p -> {
            return Country.ITALY.equals(((User) p).getCountry());
        };

        this.users.stream().filter(italy).forEach((person) -> {
            System.out.print(((User) person).getCountry());
            System.out.println(((User) person).getAge());
        });
        //not older then 5
        User us =  this.users.stream().filter(person -> {
            return Country.ITALY.equals(person.getCountry()) && person.getAge() < 5;
        }).max(Comparator.comparing(User::getAge)).get();

        System.out.println(us.getAge());
    }

    public static void main(String[] args) {
        new App();
    }
}

Country.java

/**
 * Created by iliesa on 22.09.2016.
 */
public interface Country {
    static String SPAIN = "Spain";
    static String ITALY = "Italy";
    static String IRELAND = "Ireland";
}

SimpleLambdaExamples.java

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.function.BiFunction;

/**
 * Created by iliesa on 22.09.2016.
 */
public class SimpleLamdaExamples {

    public static void main(String[] args) {
        new SimpleLamdaExamples().example3();
    }

    public void example1() {
        BiFunction addition = (x, y) -> (int) x + (int) y;
        System.out.println("result: " + addition.apply(1, 5));
    }

    public void example2() {
        Arrays.asList("e1", "e1", "e3", "e4").forEach(e -> System.out.println(e));
    }

    public void example3()
    {
        ArrayList<String> arrayList = new ArrayList((Arrays.asList("e1", "e1", "e3f", "e3")));
        Collections.sort(arrayList,(String a, String b) -> b.compareTo(a) );
        arrayList.forEach(e-> System.out.println(e));
    }
}

User.java

/**
 * Created by iliesa on 22.09.2016.
 */
public class User {
    private String usename;
    private int age;
    private String country;

    public User(String usename, int age, String country) {
        this.usename = usename;
        this.age = age;
        this.country = country;
    }

    public String getUsername() {
        return usename;
    }

    public void setUsename(String usename) {
        this.usename = usename;
    }

    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;
    }
}