global  _main
        extern  _printf

        section .text
_main:
        push    message
        call    _printf
        add     esp, 4
        ret
message:
        db      'Hello, World', 10, 0

#include <stdio.h>

int main() {
   printf("Hello, World");
   return 0;
}

#include <stdlib.h>

void f(int n)
{
  int* array = calloc(n, sizeof(int));
  do_some_work(array);
}

class Main {
    public static void main(String[] args) {
        int a = 45;
        int b = 55;
        System.out.println(sum(a, b));
    }

    public static int sum(int a, int b) {
        return a + b;
    }
}

def sum(a, b):
    return a + b


if __name__ == '__main__':
    a = 45
    b = 55
    print(sum(a, b))

class Main {
    public static void main(String[] args) {
        var a = 45;
        var b = 55;
        System.out.println(sum(a, b));
    }

    public static int sum(int a, int b) {
        return a + b;
    }
}

class Main {
    public static void main(String[] args) {
        var temp = "some_string";
        // ошибка компиляции: temp типа String, нельзя присвоить int
        temp = 78;
        var a = 45;
        var b = "55";
        System.out.println(
            // ошибка компиляции: b типа String, но ожидался int
            sum(a, b)
        );
    }

    public static int sum(int a, int b) {
        return a + b;
    }
}

s = "Hello, World"
s1 = {
    'key': 'value'
}
# TypeError:  unsupported operand type(s) for +: 'dict' and 'str'
result_str = s + s1

s = "Hello, World"
s1 = {
    'key': 'value'
}
# {'key': 1}d"
result_str = s + str(s1)

const s = "Hello, World";
const s1 = {
    key: 'value'
}
// Hello, World[object Object]
result_str = s + s1;

[] == ![];
+[] == +![];
0 == +false
0 == false
false == []
false == ![]

0 === false; // false
false === [] // false
0 === 0 // true

class Main {
    public static void main(String[] args) {
        int i = 12;
        double d = 13.5;
        // d == 12.0
        d = i;
    }
}

class Main {
    public static void main(String[] args) {
        int i = 12;
        double d = 13.5;
        // incompatible types: possible lossy conversion from double to int
        i = d;
    }
}

class Main {
    public static void main(String[] args) {
        // abc10
        System.out.println("abc" + 10);
    }
}

-- Без явного указания типа
add (x, y) = x + y

-- Явное указание типа
add :: (Integer, Integer) -> Integer
add (x, y) = x + y

public class Main { // (1)

  public static void main(String[] args) { // (2), (4)
    System.out.println("Hello, world!");   // (3)
  } // (4)
}

Hello, world!

package org.example;

public class Car {

}

package org.example;

public class Car {

  public String brand;
  public int year;
  public String color;
}

public class Main {

  public static void main(String[] args) {
    Car car = new Car();
    car.brand = "Lada";
    car.year = 2023;
    car.color = "Красный";

    System.out.println("Бренд: " + car.brand);
    System.out.println("Год выпуска: " + car.year);
    System.out.println("Цвет: " + car.color);
  }
}

Бренд: Lada
Год выпуска: 2023
Цвет: Красный

public class Main {

  public static void main(String[] args) {
    int myNum = 10;
    printNumber(myNum);
    System.out.println(myNum);
  }
  
  public static void printNumber(int number) {
    number = number + 10;
    System.out.println(number);
  }
}

public class Main {

  public static void main(String[] args) {
    Car car = new Car();
    car.brand = "Lada";
    printCar(car);
    System.out.println(car.brand);
  }
  
  public static void printCar(Car car) {
    car.brand = "Moskvich";
    System.out.println(car.brand);
  }
}

public class Main {

  public static void main(String[] args) {
    Car car = new Car();
    car.brand = "Lada";
    printCar(car);
    System.out.println(car.brand);
  }
  
  public static void printCar(Car car) {
    car = new Car();
    car.brand = "Moskvich";
    System.out.println(car.brand);
  }
}

public class CarUtil {

  public static void print(Car car) {
    System.out.println("Бренд: " + car.brand);
    System.out.println("Год выпуск: " + car.year);
    System.out.println("Цвет: " + car.color);
  }
}

public class Car {

  public String brand;
  public int year;
  public String color;

  public void print() {
    System.out.println("Бренд: " + this.brand);
    System.out.println("Год выпуск: " + this.year);
    System.out.println("Цвет: " + this.color);
  }
}

public class Main {

  public static void main(String[] args) {
    Car car = new Car();
    car.brand = "Lada";
    car.year = 2023;
    car.color = "Красный";

    CarUtil.print(car);
    car.print();
  }
}

public class Car {
    public String brand;
    public int year;
    public String color;

    public Car(String brand, int year, String color) {
        this.brand = brand;
        this.year = year;
        this.color = color;
    }

    public void print() {
        System.out.println("Бренд: " + this.brand);
        System.out.println("Год выпуск: " + this.year);
        System.out.println("Цвет: " + this.color);
    }
}

public class Main {
    public static void main(String[] args) {
        Car car = new Car("Lada", 2023, "Красный");
        car.print();
    }
}

public class Car {
    private String brand;
    private int year;
    private String color;

    public Car(String brand, int year, String color) {
        this.brand = brand;
        this.year = year;
        this.color = color;
    }

    public void print() {
        System.out.println("Бренд: " + this.brand);
        System.out.println("Год выпуск: " + this.year);
        System.out.println("Цвет: " + this.color);
    }
}

public class Car {
    private String brand;
    private int year;
    private String color;

    public Car(String brand, int year, String color) {
        this.brand = brand;
        this.year = year;
        this.color = color;
    }

    public void print() {
        System.out.println("Бренд: " + this.brand);
        System.out.println("Год выпуск: " + this.year);
        System.out.println("Цвет: " + this.color);
    }

    public String getBrand() {
        return brand;
    }

    public int getYear() {
        return year;
    }

    public String getColor() {
        return color;
    }
}

public class Car {
    private String brand;
    private int year;
    private String color;

    public Car(String brand, int year, String color) {
        this.brand = brand;
        this.year = year;
        this.color = color;
    }

    public void print() {
        System.out.println("Бренд: " + this.brand);
        System.out.println("Год выпуск: " + this.year);
        System.out.println("Цвет: " + this.color);
    }

    public void setBrand(String brand) {
        this.brand = brand;
    }

    public void setYear(int year) {
        this.year = year;
    }

    public void setColor(String color) {
        this.color = color;
    }
}

public class Car {
    /* поля и конструктор */
  
    public void setBrand(String brand) {
        if (brand.length() < 50) {
            this.brand = brand;
        }
    }
}

public class Car {
    /* поля и конструктор */

    public Car withBrand(String newBrand) {
        return new Car(newBrand, this.year, this.color);
    }
}

public class Main {
    public static void main(String[] args) {
        Car car = new Car("Lada", 2023, "Красный");
        Car newCar =
            car.withBrand("Moskvich")
                    .withYear(1965)
                    .withColor("Белый");
        newCar.print();
    }
}

Бренд: Moskvich
Год выпуск: 1965
Цвет: Белый

public class Car {
    private final String brand;
    private final int year;
    private final String color;

    public Car(String brand, int year, String color) {
        this.brand = brand;
        this.year = year;
        this.color = color;
    }

    public void print() {
        System.out.println("Бренд: " + this.brand);
        System.out.println("Год выпуск: " + this.year);
        System.out.println("Цвет: " + this.color);
    }
}

public class Airplane {
    private final int year;
    private final String color;

    public Airplane(int year, String color) {
        this.year = year;
        this.color = color;
    }

    public void print() {
        System.out.println("Год выпуска самолета: " + this.year);
        System.out.println("Цвет самолета: " + this.color);
    }
}

public class Vehicle {
    protected final int year;
    protected final String color;

    public Vehicle(int year, String color) {
        this.year = year;
        this.color = color;
    }
}

public class Airplane extends Vehicle {
    public Airplane(int year, String color) {
        super(year, color);
    }

    public void print() {
        System.out.println("Год выпуска самолета: " + this.year);
        System.out.println("Цвет самолета: " + this.color);
    }
}

public class Car extends Vehicle {
    private final String brand;

    public Car(String brand, int year, String color) {
        super(year, color);
        this.brand = brand;
    }

    public void print() {
        System.out.println("Бренд: " + this.brand);
        System.out.println("Год выпуска: " + this.year);
        System.out.println("Цвет: " + this.color);
    }
}

public class VehicleUtil {
    public static void printVehicle(Vehicle vehicle) {
        System.out.println("Выводим информацию о технике");
        vehicle.print();
    }
}

public class Vehicle {
  protected final int year;
  protected final String color;

  public Vehicle(int year, String color) {
    this.year = year;
    this.color = color;
  }
  
  public void print() {
    // do nothing
  }
}

public class Main {
    public static void main(String[] args) {
        Car car = new Car("Lada", 2023, "Красный");
        Airplane airplane = new Airplane(1980, "Boeing");
        VehicleUtil.printVehicle(car);
        VehicleUtil.printVehicle(airplane);
    }
}

Выводим информацию о технике
Бренд: Lada
Год выпуск: 2023
Цвет: Красный
Выводим информацию о технике
Год выпуска самолета: 1980
Цвет самолета: Boeing

public abstract class Vehicle {
    protected final int year;
    protected final String color;

    public Vehicle(int year, String color) {
        this.year = year;
        this.color = color;
    }

    public abstract void print();
}

public class Main {
    public static void main(String[] args) {
        Vehicle vehicle = new Vehicle(1983, "Ford");
        vehicle.print();
    }
}

public interface Vehicle {
    void print();
}

public class Car implements Vehicle {
    private final String brand;
    private final int year;
    private final String color;

    public Car(String brand, int year, String color) {
        this.brand = brand;
        this.year = year;
        this.color = color;
    }

    @Override
    public void print() {
        System.out.println("Бренд: " + this.brand);
        System.out.println("Год выпуска: " + this.year);
        System.out.println("Цвет: " + this.color);
    }
}

public class Main {
    public static void main(String[] args) {
        Vehicle vehicle = new Vehicle(1983, "Ford");
        vehicle.print();
    }
}

public class Main {
    public static void main(String[] args) {
        Vehicle vehicle = new Vehicle() {
            @Override
            public void print() {
              System.out.println("Машина Ford 1983 года");
            }
        };
        vehicle.print();
    }
}

public class Main {
    public static void main(String[] args) {
        Vehicle vehicle = () -> System.out.println("Машина Ford 1983 года");
        vehicle.print();
    }
}

public enum VehicleType {
  CAR,
  SHIP
}

public class Vehicle {

  public void move(VehicleType vehicleType) {
    switch (vehicleType) {
      case CAR:
        System.out.println("Driving");
        break;
      case SHIP:
        System.out.println("Sailing");
        break;
    }
  }
}

Integer x=1;          // autoboxing
int y=new Integer(1); // unboxing

public class Person {
  private final String firstName;
  private final String lastName;
  private final String patronymic;

  /* конструктор */
}

public class Main {
    public static void main(String[] args) {
        Person person = new Person("Петр", "Иванов", null);
        System.out.println(person);
    }
}

public class Main {
    public static void main(String[] args) {
        Airplane airplane = new Airplane(1980, "TU-154");
        airplane = null;
        airplane.print();
    }
}

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "org.example.Airplane.print()" because "airplane" is null
	at org.example.Main.main(Main.java:8)

class Object {
    /* other methods... */
  
    public boolean equals(Object obj) {
        return (this == obj);
    }
}

public class Main {
    public static void main(String[] args) {
        Airplane airplane1 = new Airplane(1980, "RED");
        Airplane airplane2 = airplane1;
        System.out.println(airplane1.equals(airplane2));
    }
}

public class Main {
    public static void main(String[] args) {
        Airplane airplane1 = new Airplane(1980, "RED");
        Airplane airplane2 = new Airplane(1980, "RED");
        System.out.println(airplane1.equals(airplane2));
    }
}

public class Airplane {
  /* поля и конструктор */ 
  
  @Override
  public boolean equals(Object o) {
    if (o instanceof Airplane airplane) {
      return year == airplane.year && Objects.equals(color, airplane.color);
    }
    return false;
  }
}

public class Objects {
    public static boolean equals(Object a, Object b) {
        return (a == b) || (a != null && a.equals(b));
    }
}

public class Main {
    public static void main(String[] args) {
        Airplane airplane1 = new Airplane(1980, "TU-154");
        Airplane airplane2 = new Airplane(1980, "TU-154");
        System.out.println(airplane1.equals(airplane2));
    }
}

public class Object {
    public native int hashCode();
}

public class Main {
    public static void main(String[] args) {
        Airplane airplane1 = new Airplane(1980, "TU-154");
        Airplane airplane2 = new Airplane(1980, "TU-154");
        System.out.println("HashCode для Airplane1: " + airplane1.hashCode());
        System.out.println("HashCode для Airplane2: " + airplane2.hashCode());
    }
}

HashCode для Airplane1: -1810167607
HashCode для Airplane2: -1810167607

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

public class Main {
    public static void main(String[] args) {
        Airplane airplane1 = new Airplane(1980, "TU-154");
        Airplane airplane2 = new Airplane(1990, "Boeing");
        Map<Airplane, Integer> map = new HashMap<>();
        map.put(airplane1, 2);
        map.put(airplane2, 3);
  }
}

public class Main {
    public static void main(String[] args) {
        Airplane airplane1 = new Airplane(1980, "TU-154");
        Airplane airplane2 = new Airplane(1990, "Boeing");
        Map<Airplane, Integer> map = new HashMap<>();
        map.put(airplane1, 2);
        map.put(airplane2, 3);

        System.out.println(map.get(new Airplane(1980, "TU-154")));
        System.out.println(map.get(new Airplane(1990, "Boeing")));
  }
}

public class Object {
    public String toString() {
        return getClass().getName() + "@" + Integer.toHexString(hashCode());
    }
}

public class Car implements Vehicle {
    /* Поля и конструктор */
  
    @Override
    public String toString() {
        return String.format("Car[brand=%s, year=%d, color=%s]", this.brand, this.year, this.color);
    }
}

public class Main {
    public static void main(String[] args) {
        Car car = new Car("Toyota", 2009, "WHITE");

        System.out.println("Машина: " + car.toString());
        System.out.println("Машина: " + car);
    }
}

public class Airplane implements Vehicle {
    /* поля и конструктор */

    public Airplane(int year, String color) {
        if (color == null) {
            throw new RuntimeException("Color cannot be null");
        }
        this.year = year;
        this.color = color;
    }
}

public class Main {
    public static void main(String[] args) {
        Airplane airplane = new Airplane(1980, null);
        airplane.print();
    }
}

Exception in thread "main" java.lang.RuntimeException: Color cannot be null
	at org.example.Airplane.<init>(Airplane.java:12)
	at org.example.Main.main(Main.java:9)

public class Main {
    public static void main(String[] args) {
        try {
            Airplane airplane = new Airplane(1980, null);
            airplane.print();
        } catch (RuntimeException e) {
            System.out.println("Ошибка при создании Airplane");
        }
    }
}

public class Main {
    public static void main(String[] args) {
        try {
            Airplane airplane = new Airplane(1980, null);
            airplane.print();
        } catch (Exception e) {
            System.out.println("Ошибка при создании Airplane");
        }
    }
}

public class Airplane implements Vehicle {
    /* поля и конструктор */
  
    public Airplane withYear(int newYear) {
        if (newYear < 0) {
            throw new RuntimeException("Year cannot be less than zero: " + newYear);
        }
        return new Airplane(newYear, this.color);
    }
}

public class Airplane implements Vehicle {
    /* поля и конструктор */
  
    public Airplane withYear(int newYear) {
        if (newYear < 0) {
            throw new Exception("Year cannot be less than zero: " + newYear);
        }
        return new Airplane(newYear, this.color);
    }
}

public class Airplane implements Vehicle {
    /* поля и конструктор */
  
    public Airplane withYear(int newYear) throws Exception {
        if (newYear < 0) {
            throw new Exception("Year cannot be less than zero: " + newYear);
        }
        return new Airplane(newYear, this.color);
    }
}

public class Main {
    public static void main(String[] args) {
        Airplane airplane = new Airplane(1980, "RED");
        Airplane newAirplane = airplane.withYear(2000);
        newAirplane.print();
    }
}

public class Main {
    public static void main(String[] args) {
        Airplane airplane = new Airplane(1980, "RED");
        try {
            Airplane newAirplane = airplane.withYear(2000);
            newAirplane.print();
        } catch (Exception e) {
            System.out.println("Ошибка при создании нового Airplane");
        }
    }
}

public class Airplane implements Vehicle {
    /* поля и конструктор */

    public Airplane(int year, String color) {
        if (color == null) {
            throw new IllegalArgumentException("Color cannot be null");
        }
        this.year = year;
        this.color = color;
    }
}

public class Main {
   public static void main(String[] args) {
      Airplane airplane = new Airplane(1980, null);
      airplane.print();
   }
}

Exception in thread "main" java.lang.RuntimeException: Color cannot be null
	at org.example.Airplane.<init>(Airplane.java:12)
	at org.example.Main.main(Main.java:6)

public class Airplane implements Vehicle {
    /* поля и конструктор */

    public Airplane(int year, String color) {
        if (color == null) {
            throw new IllegalArgumentException("Color cannot be null");
        }
        this.year = year;
        this.color = color;
    }
}

public class Main {
   public static void main(String[] args) {
     try {
         Airplane airplane = new Airplane(1980, null);
         airplane.print();
     }
     catch (IllegalArgumentException e) {
         throw new IllegalStateException("Couldn't create Airplane");
     }
   }
}

Exception in thread "main" java.lang.IllegalStateException: Couldn't create Airplane
	at org.example.Main.main(Main.java:11)

public class Airplane implements Vehicle {
    /* поля и конструктор */

    public Airplane(int year, String color) {
        if (color == null) {
            throw new IllegalArgumentException("Color cannot be null");
        }
        this.year = year;
        this.color = color;
    }
}

public class Main {
   public static void main(String[] args) {
     try {
         Airplane airplane = new Airplane(1980, null);
         airplane.print();
     }
     catch (IllegalArgumentException e) {
         // в переменной 'e' хранится объект исключения, который был выброшен
         throw new IllegalStateException("Couldn't create Airplane", e); // передаем 'e' вторым параметром
     }
   }
}

Exception in thread "main" java.lang.IllegalStateException: Couldn't create Airplane
	at org.example.Main.main(Main.java:11)
Caused by: java.lang.IllegalArgumentException: Color cannot be null
	at org.example.Airplane.<init>(Airplane.java:12)
	at org.example.Main.main(Main.java:7)

public class Container {
    private final Car value;

    public Container(Car value) {
        this.value = value;
    }

    public boolean isPresent() {
        return value != null;
    }

    public void print() {
        if (isPresent()) {
            System.out.println("Container value is: " + value);
        } else {
            System.out.println("Container is empty");
        }
    }

    public Car getValue() {
        return value;
    }
}

public class Container {
    private final Object value;

    public Container(Object value) {
        this.value = value;
    }

    public boolean isPresent() {
        return value != null;
    }

    public void print() {
        if (isPresent()) {
            System.out.println("Container value is: " + value);
        } else {
            System.out.println("Container is empty");
        }
    }

    public Object getValue() {
        return value;
    }
}

public class Main {
    public static void main(String[] args) {
        Container container = new Container(new Car(...));
        /* некоторая логика работы */
        Car car = (Car) container.getValue();
    }
}

public class Main {
    public static void main(String[] args) {
        String str = "abc";
        Object obj = (Object) str;
        LocalDate date = (LocalDate) obj;
    }
}

Exception in thread "main" java.lang.ClassCastException: class java.lang.String cannot be cast to class java.time.LocalDate (java.lang.String and java.time.LocalDate are in module java.base of loader 'bootstrap')
	at org.example.Main.main(Main.java:10)

public class Container<T> {
    private final T value;

    public Container(Object value) {
        this.value = value;
    }

    public boolean isPresent() {
        return value != null;
    }

    public void print() {
        if (isPresent()) {
            System.out.println("Container value is: " + value);
        } else {
            System.out.println("Container is empty");
        }
    }

    public T getValue() {
        return value;
    }
}

public class Main {
    public static void main(String[] args) {
        Container<Car> container = new Container<>(new Car(...));
        /* некоторая логика работы */
        Car car = container.getValue();
    }
}

public class Main {
    public static void main(String[] args) {
        int value = getInt();
        printInt(value);
    }
  
    private static Integer getInt() {
        return 10;
    }
  
    private static void printInt(Integer value) {
        System.out.println(value);
    }
}

public class Main {
    public static void main(String[] args) {
        Integer valueObj = getInt();
        int value = valueObj.intValue();
        printInt(Integer.valueOf(value));
    }
  
    private static Integer getInt() {
        return Integer.valueOf(10);
    }
  
    private static void printInt(Integer value) {
        System.out.println(value);
    }
}

public class Main {
    public static void main(String[] args) {
        printInt(null);
    }
  
    private static void printInt(int value) {
        System.out.println(value);
    }
}

public class Main {
    public static void main(String[] args) {
        Integer valueObj = null;
        printInt(valueObj);
    }
  
    private static void printInt(int value) {
        System.out.println(value);
    }
}

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "java.lang.Integer.intValue()" because "valueObj" is null
	at org.example.Main.main(Main.java:9)

public interface Iterator<E> {
  boolean hasNext();
  
  E next();
  
  default void remove() {
    throw new UnsupportedOperationException("remove");
  }
  
  default void forEachRemaining(Consumer<? super E> action) {
    Objects.requireNonNull(action);
    while (hasNext())
      action.accept(next());
  }
}

public class IterableExample {
    public void iterate(Iterable<String> iterable) {
        Iterator<String> iterator = iterable.iterator();
        while (iterator.hasNext()) {
            String element = iterator.next();
            System.out.println("Current element: " + element);
        }
    }
}

public class IterableExample {
    public void iterate(Iterable<String> iterable) {
        for (String element : iterable) {
            System.out.println("Current element: " + element);
        }
    }
}

public class ListExample {
    public void iterate(List<String> list) {
        for (int i = 0; i < list.size(); i++) {
            System.out.println("index = " + i);
            System.out.println("element = " + list.get(i));
        }
    }
}

public class MapExample {
    public void iterate(Map<String, Integer> map) {
        for (Map.Entry<K, V> entry : map.entrySet()) {
            System.out.printf("Key = %s, value = %d %n", entry.getKey(), entry.getValue()); 
        }
    }
}

public class MapExample {
    public void iterate(Map<String, Integer> map) {
        for (String key : map.keySet()) {
            int value = map.get(key); 
            System.out.printf("Key = %s, value = %d %n", entry.getKey(), entry.getValue()); 
        }
    }
}

public class MapExample {
    public void iterate(Map<String, Integer> map) {
        map.forEach((k, v) -> System.out.printf("Key = %s, value = %d %n", k, v));
    }
}

public class Main {
    public static void main(String[] args) {
        List<String> list = new ArrayList<>();
        list.add(1);
        list.add(2);
        list.add(1);
        System.out.println(list);
    }
}

public class Main {
    public static void main(String[] args) {
        Set<String> set = new HashSet<>();
        set.add(1);
        set.add(2);
        set.add(1);
        System.out.println(set);
    }
}

public class Main {
    public static void main(String[] args) {
        Map<Integer, String> map = new HashMap<>();
        map.put(1, "Bob");
        map.put(2, "Alice");
        System.out.println(map);
    }
}

public class Main {
  public static void main(String[] args) {
      String[] arr = new String[20];
      for (int i = 0; i < arr.length; i++) {
          arr[i] = "Str" + i;
      }
  }
}

public class Airplane {
    private final int year;
    private final String color;

    public Airplane(int year, String color) {
        this.year = year;
        this.color = color;
    }
    
    /* другие методы */
}

public class Color {
    public static final String WHITE = "WHITE";
    public static final String BLUE = "BLUE";
}

public class Main {
    public static void main(String[] args) {
        Airplane airplane = new Airplane(1985, Color.WHITE);
        /* действия с airplane... */
    }
}

public class Main {
    public static void main(String[] args) {
        Airplane airplane1 = new Airplane(1985, Color.WHITE);
        Airplane airplane2 = new Airplane(1985, "white");
        System.out.println(airplane1.equals(airplane2));
    }
}

public enum Color {
    WHITE, BLUE;
}

public class Color extends Enum<Color> {
    public static final Color WHITE = new Color("WHITE", 0);
    public static final Color BLUE = new Color("BLUE", 1);
    
    private Color(String name, int ordinal) {
        super(name, ordinal);
    }
    
    /* другие методы из класса Enum */
}

public enum Color {
    WHITE("белый"), BLUE("синий");
  
    private final String ru;

    Color(String ru) {
        this.ru = ru;
    }

    public String getRu() {
        return ru;
    }
}

public enum Color {
    WHITE("белый"), BLUE("синий");
  
    private final String ru;

    Color(String ru) {
        this.ru = ru;
    }

    public String getRu() {
        return ru;
    }
}

public class Main {
    public static void main(String[] args) {
        for (Color color : Color.values()) {
            System.out.println(color.getRu());
        }
    }
}

public class Airplane {
    private final int year;
    private final Color color;

    public Airplane(int year, String color) {
        this.year = year;
        this.color = color;
    }
    
    /* другие методы */
}

public class Main {
    public static void main(String[] args) {
        Airplane airplane = new Airplane(1985, Color.WHITE);
        /* действия с airplane... */
    }
}

public class Main {
    public static void main(String[] args) {
        Airplane airplane1 = new Airplane(1985, Color.WHITE);
        Airplane airplane2 = new Airplane(1985, "white"); // COMPILE ERROR!
        System.out.println(airplane1.equals(airplane2));
    }
}

public class CustomerRepository {
    /* поля и конструктор */
  
    public Customer findById(CustomerId id) {
        if (!existsById(id)) {
            return null;
        }
        /* логика поиска Customer по id */
    }
}

public class Main {

  public static void main(String[] args) {
    CustomerRepository customerRepository = createCustomerRepository();
    Customer customer = customerRepository.findById(new CustomerId(1));
    System.out.println(customer.getSalary());
  }

  private static CustomerRepository createCustomerRepository() {
    /* логика создания CustomerRepository */
  }
}

public class CustomerRepository {
    /* поля и конструктор */
  
    public Optional<Customer> findById(CustomerId id) {
        if (!existsById(id)) {
            return Optional.empty();
        }
        /* логика поиска Customer по id */
        return Optional.ofNullable(customer);
    }
}

public class Main {

  public static void main(String[] args) {
      CustomerRepository customerRepository = createCustomerRepository();
      Optional<Customer> customer = customerRepository.findById(new CustomerId(1));
      if (customer.isPresent()) {
          Customer value = customer.get();
          System.out.println(customer.getSalary());
      }
  }

  private static CustomerRepository createCustomerRepository() {
    /* логика создания CustomerRepository */
  }
}