Primitive Obsession with Example

Primitive Obsession is the name of a code smell that occurs when we use primitive data types to represent domain ideas. For example, we use a string to represent a message or an integer to represent an amount of money.
For Example: Code with Primitive Obsession

// primitiveObsession.java

public class primitiveObsession {

	public static void main(String args[]) {

		Integer[] cityPopulations = { 13000000, // London
				21903623, // New York
				12570000, // Tokyo
				1932763, // Stockholm
				1605602, // Barcelona
				4119190 // Sydney
		};

		for (Integer cityPopulation : cityPopulations) {
			System.out.println(cityPopulation);
		}

	}

}

public class City {

	private final String name;
	private final int population;
	private final Continent continent;

	public String getName() {
		return name;
	}

	public int getPopulation() {
		return population;
	}

	public Continent getContinent() {
		return continent;
	}

	public City(String name, int population, Continent continent) {
		this.name = name;
		this.population = population;
		this.continent = continent;
	}

	public String toString() {
		return String.format("%s has a popluation of %s and is located in %s",
				name, population, continent);
	}

	public static final City[] ALL_CITIES = { 
			new City("London", 13000000, Continent.EUROPE),
			new City("New York", 21903623, Continent.AMERICA), 
			new City("Tokyo", 12570000, Continent.ASIA),
			new City("Stockholm", 1932763, Continent.EUROPE), 
			new City("Barcelona", 1605602, Continent.EUROPE),
			new City("Sydney", 4119190, Continent.AUSTRALIA)
	};

}

//Continent.java

public enum Continent {
	AMERICA,
	EUROPE,
	AFRICA,
	ASIA,
	AUSTRALIA
}

// withOutPrimitiveObsession.java

public class withOutPrimitiveObsession {

	public static void main(String args[]) {

		for (City city : City.ALL_CITIES) {
			System.out.println(city.toString());
		}

	}

}