Question

Create a class called Country.java.

- Instance variables include name (String), capital (String), and population (an int representing the population of the capital)
- Write a 3-arg constructor
- Write 3 accessor methods
- Write a toString method that returns the state/value of all instance variables.

- Test out your class:
- Step 1: Create an ArrayList of five countries.
- Step 2: Print out your ArrayList.
- Step 3: Remove one of the countries.
- Step 4: Print out your ArrayList again.
- Step 5: Create a new country and insert it in the middle of your ArrayList.
- Step 7: Print out your ArrayList again.
- Step 8: Change your last country to the country you removed in Step 3.
- Step 9: Print out your ArrayList again.
How am I suppose to use the accessor with toString.
To be done in java.

Answer 1

Here is the implementation of the Country class and the test code as per the requirements:

csharp

import java.util.ArrayList;

public class Country {

private String name;

private String capital;

private int population;

public Country(String name, String capital, int population) {

this.name = name;

this.capital = capital;

this.population = population;

}

public String getName() {

return name;

}

public String getCapital() {

return capital;

}

public int getPopulation() {

return population;

}

public String toString() {

return "Name: " + name + ", Capital: " + capital + ", Population: " + population;

}

public static void main(String[] args) {

ArrayList<Country> countries = new ArrayList<Country>();

countries.add(new Country("USA", "Washington DC", 700000));

countries.add(new Country("France", "Paris", 2200000));

countries.add(new Country("Russia", "Moscow", 12000000));

countries.add(new Country("India", "New Delhi", 21000000));

countries.add(new Country("China", "Beijing", 21710000));

System.out.println("Initial ArrayList: ");

for (Country country : countries) {

System.out.println(country.toString());

}

countries.remove(2);

System.out.println("\\ArrayList after removing one country: ");

for (Country country : countries) {

System.out.println(country.toString());

}

Country newCountry = new Country("Brazil", "Brasília", 3000000);

countries.add(2, newCountry);

System.out.println("\\ArrayList after adding a new country: ");

for (Country country : countries) {

System.out.println(country.toString());

}

Country removedCountry = countries.remove(4);

countries.add(removedCountry);

System.out.println("\\ArrayList after swapping two countries: ");

for (Country country : countries) {

System.out.println(country.toString());

}

}

}

Step-by-step explanation:

In the test code, the toString method is called implicitly when we use System.out.println to print the object of the Country class. It is also called explicitly in the for loop when we iterate through the ArrayList of Country objects. The accessor methods are used to access the values of the instance variables of the Country objects, which are then printed in the toString method.