Main.java - master - digit/java-core-StreamAPI

Main.java
91 строка3 KB
digit
Create: Calculator.java, Education.java, Main.java, OnTaskDoneListener.java, Person.java, README (task 1).md, README (task 2).md, Sex.java, Worker.java
09 авг 2026, 21:58
Верифицирован
09 авг 2026, 21:58eb4f912
import java.util.*;

public class Main {
    public static void main(String[] args) {
        // Calculator
        Calculator calc = Calculator.instance.get();
        int a = calc.plus.apply(1, 2);
        int b = calc.minus.apply(1, 1);
        try {
            int c = calc.divide.apply(a, b); // division by zero
            calc.println.accept(c);
        } catch (ArithmeticException e) {
            System.out.println(e.getMessage());
        }
        System.out.println();

        // Worker
        OnTaskDoneListener listener = System.out::println;
        Worker worker = new Worker(listener);
        worker.start();
        System.out.println();

        // Working with numbers
        var numbers = new ArrayList<>(List.of(1, 2, 5, 16, -1, -2, 0, 32, 3, 5, 8, 23, 4));

        // Without Stream API
        ArrayList<Integer> numbersWithoutStreamAPI = new ArrayList<>(numbers);
        for (Iterator<Integer> it = numbersWithoutStreamAPI.iterator(); it.hasNext(); ) {
            int num = it.next();
            if (num <= 0 || num % 2 != 0) {
                it.remove();
            }
        }
        numbersWithoutStreamAPI.sort(Integer::compareTo);
        for (Integer number : numbersWithoutStreamAPI) {
            System.out.println(number);
        }
        System.out.println();

        // With Stream API
        ArrayList<Integer> numbersWithStreamAPI = new ArrayList<>(numbers);
        numbersWithStreamAPI.stream()
                .filter(x -> x > 0)
                .filter(x -> x % 2 == 0)
                .sorted(Comparator.naturalOrder())
                .forEach(System.out::println);
        System.out.println();

        // Population census
        List<String> names = Arrays.asList("Jack", "Connor", "Harry", "George", "Samuel", "John");
        List<String> families = Arrays.asList("Evans", "Young", "Harris", "Wilson", "Davies", "Adamson", "Brown");
        Collection<Person> persons = new ArrayList<>();
        for (int i = 0; i < 10_000_000; i++) {
            persons.add(new Person(
                    names.get(new Random().nextInt(names.size())),
                    families.get(new Random().nextInt(families.size())),
                    new Random().nextInt(100),
                    Sex.values()[new Random().nextInt(Sex.values().length)],
                    Education.values()[new Random().nextInt(Education.values().length)])
            );
        }

        System.out.println(
                persons.stream()
                .filter(p -> p.getAge() < 18)
                .count()
        );
        System.out.println();

        List<String> surnames = persons.stream()
                .filter(p -> p.getAge() >= 18 && p.getAge() < 27)
                .map(Person::getName)
                .toList();
        for (int i = 0; i < Math.min(5, surnames.size()); i++) {
            System.out.println(surnames.get(i));
        }
        System.out.println();

        List<String> workingSurnames = persons.stream()
                .filter(p -> p.getEducation() == Education.HIGHER)
                .filter(p -> p.getAge() >= 18)
                .filter(p -> p.getSex() == Sex.WOMAN && p.getAge() <= 60
                        || p.getSex() == Sex.MAN && p.getAge() <= 65)
                .map(Person::getFamily)
                .sorted()
                .toList();
        for (int i = 0; i < Math.min(5, workingSurnames.size()); i++) {
            System.out.println(workingSurnames.get(i));
        }
    }
}