Question

2. Create ONE java file in Dr Java according the specifications below: A. Create a Country class a. Each Country object of the Country class should know (state) i. its name ii. its area (in square miles) iii. its population b. Each Country object should be able to (behavior) i. set initial population (setter) ii. get density (number of people per square mile) (getter) iii. adjust the set population by some amount (setter) iv. provide its name, area, and population (toString() using getters - see below*) B. In the main() method, create at least two Country objects and make sure each object uses ALL methods from the Country class. * Reference variables in Java contain the memory address of an object, so the command System.out.print (obj); with objbeing a reference variable, will return the memory address of the referenced object , i.e. Country@33223e60 Instead, we can use the inherited Object class's toString() method to print out values from the object by using the getters. Here's an example of a toString() for a person class: public String toString() { return "The person's name is 11 11 + getName() + " and age is + getAge() + "."); } Once the toString() method is added as one of the class methods, the command System.out.print(obj);, will then print out something like the person's name is Sam and age is 16.

Answer 1

Program Code Screenshot :

1 2 Main.java class Country{ //Private instance variables private String name; private double area; private int population; 3 4 5 6 7 00 //Set initial population public void setInitialPopulation(int population){ this.population = population; 9 19 } 11 12 13 //Return the density public double getDensity ({ return population/area; 14 15 } 16 17 18 //Adjust the population public void adjust(int delta){ this.population += delta; 19 20 } 21 22 23 //Getter and Setter public String getName() { return name; 24 25 هه 26 27 public void setName(String name) { this.name = name; 28 29 } 30 31 public double getArea() { return area; 32 33 } 34 35 public void setArea (double area) { this.area = area; 36 37 } 38 39 public int getPopulation () { return this.population; 40 41 } 42 43 44 of @Override public String toString() { return "This country's name is "+getName()+" , 45 area is "+getArea()+" and Population is "+getPopulation()+".";

46 } 47 48 49 50 51 52 class Main{ public static void main(String[] args) { Country C new Country(); c.setInitialPopulation (1365897); c.setName("Westeros"); c.setArea (458963); System.out.println("Density "+c.getDensity()); System.out.println(); 53 54 55 56 57 58 }

Sample Output :

Run: Main X "C:\Program Files\Java\jdk-13\bin\java.exe" Density 2.9760503570004553 This country's name is Westeros , area is 458963.0 and Population is 1365897. If Process finished with exit code o

Program Code to Copy

class Country{
    //Private instance variables
    private String name;
    private double area;
    private int population;

    //Set initial population
    public void setInitialPopulation(int population){
        this.population = population;
    }

    //Return the density
    public double getDensity(){
        return population/area;
    }

    //Adjust the population
    public void adjust(int delta){
        this.population += delta;
    }

    //Getter and Setter
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getArea() {
        return area;
    }

    public void setArea(double area) {
        this.area = area;
    }

    public int getPopulation(){
        return this.population;
    }

    @Override
    public String toString(){
        return "This Country's name is "+getName()+" , area is "+getArea()+" and Population is "+getPopulation()+".";
    }
}

class Main{
    public static void main(String[] args) {
        Country c = new Country();
        c.setInitialPopulation(1365897);
        c.setName("Westeros");
        c.setArea(458963);
        System.out.println("Density "+c.getDensity());
        System.out.println(c);
    }
}