Application to calculate the price of carpeting for retangular rooms.

CarpetCostCalculator_Calculator.java

public class Calculator {
    private Floor floor;
    private Carpet carpet;

    public Calculator(Floor floor, Carpet carpet){
        this.floor = floor;
        this.carpet = carpet;
    }

    public double getTotalCost(){
        double totalCost;
        totalCost = floor.getArea() * carpet.getCost();
        return totalCost;
    }
}

CarpetCostCalculator_Carpet.java

public class Carpet {
    private double cost;

    public Carpet (double cost){
        if (cost<0){
            this.cost = 0;
        } else {
            this.cost = cost;
        }
    }

    public double getCost(){
        return this.cost;
    }
}

CarpetCostCalculator_Floor.java

public class Floor {
    private double width;
    private double length;

    public Floor(double width, double length){
        if (width<0){
            this.width = 0;
        } else {
            this.width = width;
        }

       if (length<0){
           this.length = 0;
       } else {
           this.length = length;
       }
    }

    public double getArea (){
        return this.length * this.width;
    }
}

CarpetCostCalculator_Main.java

public class Main {

    public static void main(String[] args) {
	// testing
        Carpet carpet = new Carpet(3.5);
        Floor floor = new Floor(2.75, 4.0);
        Calculator calculator = new Calculator(floor, carpet);
        System.out.println("total = " +calculator.getTotalCost()); // 38,5

        carpet = new Carpet(1.5);
        floor = new Floor(5.4, 4.5);
        calculator = new Calculator(floor, carpet);
        System.out.println("total = " +calculator.getTotalCost()); // 36,45
    }
}