Question

Hey, I have this homework from my data structures class using java that I am having difficulties coding. I had to create an abstract class Shape, which contains two protected instance variables color(String) and filled(boolean). Getter and setter for all the instance variables, and toString(). Two abstract methods getArea() and getPerimeter().

The part that I am not sure how to code is: for the subclasses of Shape which are Circle and Rectangle I have to override the abstract methods getArea() and getPerimeter() and provide the proper implementation. They also override the toString().

Im not sure how to override getArea(), getPerimeter() and the toString(). Please help. And thanks in advance

Answer 1

public abstract class Shape {

    private String color;
    private boolean isFilled;

    public Shape() {
        this.color = "white";
        this.isFilled = true;
    }

    public Shape(String color, boolean isFilled) {
        this.color = color;
        this.isFilled = isFilled;
    }

    public String getColor() {
        return color;
    }

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

    public boolean isFilled() {
        return isFilled;
    }

    public void setFilled(boolean filled) {
        isFilled = filled;
    }

    @Override
    public String toString() {
        return "color='" + color + '\'' +
                ", isFilled=" + isFilled +
                ", area=" + getArea() +
                ", perimeter=" + getPerimeter();
    }

    public abstract double getArea();
    public abstract double getPerimeter();
}

public class Circle extends Shape {

    private double radius;

    public Circle(double radius) {
        this.radius = radius;
    }

    public Circle(String color, boolean isFilled, double radius) {
        super(color, isFilled);
        this.radius = radius;
    }

    @Override
    public double getArea() {
        return Math.PI * radius * radius;
    }

    @Override
    public double getPerimeter() {
        return 2 * Math.PI * radius;
    }
}

public class Rectangle extends Shape {

    private double width, height;

    public Rectangle(double width, double height) {
        this.width = width;
        this.height = height;
    }

    public Rectangle(String color, boolean isFilled, double width, double height) {
        super(color, isFilled);
        this.width = width;
        this.height = height;
    }

    @Override
    public double getArea() {
        return width * height;
    }

    @Override
    public double getPerimeter() {
        return 2 * (width + height);
    }
}

public class ShapeTester {

    public static void main(String[] args) {
        Circle circle = new Circle("red", true, 10);
        System.out.println(circle);
        Rectangle rectangle = new Rectangle("red", true, 10, 7);
        System.out.println(rectangle);
    }
}