Question

Purpose: The purpose of this lab is for you to design and implement several classes that use Inheritance. The problem: The program must handle a collection of different 2-dimensional shapes: triangles, rectangles and circles. All shapes have a color (use a Stringl and are either filled or not (use a boolean). All shapes must calculate and return their perimeter, and area. toStrina) for all shapes must implement the standardized formatting for inheritance. You are required to implement each of the classes below. The Shape superclasS: You must decide how best to implement the Shape superclass, as either an interface, an abstract superclass, or as full, regular inheritance. You must design and implement in Shape the most appropriate instance variables and/or methods to solve the problem. The Triangle subclass: Represents triangles. A triangle is-a shape, so inheritance must be used. Required Exactly and only 3 instance variables: private double side1; private double side2; private double side3; For simplicity, assume that any values for the 3 sides will give a valid triangle. Also that area can be calculated as: (side2/2.0) side1 You must design and implement in Triangle the most appropriate methods to solve the problem. The Rectangle subclass: Represents rectangles. A rectangle is-a shape, so inheritance must be used. Required - Exactly and only 2 instance variables: private double length; private double width; You must design and implement in Rectangle the most appropriate methods to solve the problem. The Circle subclass: Represents circles. A circle is-a shape, so inheritance must be used Required - Exactly and only 1 instance variable:

Answer 1

Here's the code for all the shapes as well as the shape abstract class and a tester class to demonstrate all the shape classes.

Shape.java (Base abstract class for all shapes):

abstract class Shape

{

protected String color;

protected boolean filled;

Shape(String color, boolean filled)

{

this.color = color;

this.filled = filled;

}

public String toString()

{

return "[color=" + this.color + ", filled=" + this.filled + "]";

}

// abstract methods to be implemented by extending classes.

public abstract double perimeter();

public abstract double area();

// setters and getters from here on.

public String getColor() {

return color;

}

public void setColor(String color) {

this.color = color;

}

public boolean isFilled() {

return filled;

}

public void setFilled(boolean filled) {

this.filled = filled;

}

}

Triangle.java:

class Triangle extends Shape

{

private double side1;

private double side2;

private double side3;

// constructor

Triangle(String color, boolean filled, double side1, double side2, double side3)

{

// calling super constructor

super(color, filled);

this.side1 = side1;

this.side2 = side2;

this.side3 = side3;

}

@Override

public double perimeter()

{

return side1 + side2 + side3;

}

@Override

public double area()

{

return (side2/2.0) * side1;

}

@Override

public String toString()

{

return "Triangle:" + super.toString() + "[side1=" + this.side1 + ", side2=" + this.side2 + ", side3=" + this.side3 + "]";

}

public double getSide1() {

return side1;

}

public void setSide1(double side1) {

this.side1 = side1;

}

public double getSide2() {

return side2;

}

public void setSide2(double side2) {

this.side2 = side2;

}

public double getSide3() {

return side3;

}

public void setSide3(double side3) {

this.side3 = side3;

}

}

Rectangle.java:

class Rectangle extends Shape

{

private double length;

private double width;

// constructor

Rectangle(String color, boolean filled, double length, double width)

{

// calling super constructor

super(color, filled);

this.length = length;

this.width = width;

}

@Override

public double perimeter()

{

return 2.0 * (length + width);

}

@Override

public double area()

{

return length * width;

}

@Override

public String toString()

{

return "Rectangle:" + super.toString() + "[length=" + length + ", width=" + width + "]";

}

public double getLength() {

return length;

}

public void setLength(double length) {

this.length = length;

}

public double getWidth() {

return width;

}

public void setWidth(double width) {

this.width = width;

}

}

Circle.java:

class Circle extends Shape

{

private double radius;

// constructor

Circle(String color, boolean filled, double radius)

{

// calling super constructor

super(color, filled);

this.radius = radius;

}

@Override

public double perimeter()

{

return 2.0 * Math.PI * radius;

}

@Override

public double area()

{

return Math.PI * Math.pow(radius, 2);

}

@Override

public String toString()

{

return "Circle:" + super.toString() + "[radius=" + this.radius + "]";

}

public double getRadius() {

return radius;

}

public void setRadius(double radius) {

this.radius = radius;

}

}

Tester.java (driver/tester class):

package shapes;

import java.util.ArrayList;

public class Tester

{

public static void main(String args[])

{

ArrayList<Shape> shapes = new ArrayList<Shape>();

// add triangle

shapes.add(new Triangle("white", true, 3.0, 2.5, 2.0));

// add rectangle.

shapes.add(new Rectangle("red", true, 2.0, 4.0));

// add circle.

shapes.add(new Circle("yellow", false, 1.0));

// print all shapes.

System.out.println("Printing all shapes");

for(Shape shape : shapes)

{

// will implicitly call toString()

System.out.println(shape);

System.out.println("Perimeter is: " + shape.perimeter());

System.out.println("Area is: " + shape.area());

}

// change the triangle filled to false.

shapes.get(0).setFilled(false);

// set the rectange color to blue.

shapes.get(1).setColor("blue");

// set the cirle color to black and change the filled to false.

shapes.get(2).setColor("black");

shapes.get(2).setFilled(false);

System.out.println("Printing all shapes after modifications");

for(Shape shape : shapes)

{

// will implicitly call toString()

System.out.println(shape);

}

}

}

Sample Output from tester class:

terminated> Tester (1) [Java Application] /usr/lib/jvm/java-11-openjdk-amd64/bin/java Printing all shapes Triangle: [color-white, filled-true][sidel-3.0, side2-2.5, side3-2.0] Perimeter is: 7.5 Area is: 3.75 Rectangle: [color-red, filled-true] [length-2.0, width-4.0] perimeter is: 12.0 Area is: 8.0 Circle :[color-yellow, filled-false] [ radius-1.0] Perimeter is: 6.283185307179586 Area is: 3.141592653589793 Printing all shapes after modifications Triangle: [color-white, filled-false][side1-3.0, side2-2.5, side3-2.0] Rectangle: [color-blue, filled-true] [length-2.0, width-4.0] Circle:[color-black, filled-false] [radius-1.0] 5 1 2