Question

Create a Bitbucket private repository.

Name it “CUS1156_Lab2”. Clone it in your local java Eclipse workspace. You will add the java files after you have completed them in Part 1 and Part 2 to this location. Part 1: Abstract classes From class, an abstract class represents some generic concept. Subclasses then provide their own specific implementations of any abstract methods of the abstract class.

1. Implement an abstract class called Shape it was discussed in the lecture. Include an abstract method double area() that returns the area of the shape.

2. Implement concrete subclasses of Shape that represents a square and a circle. Implement the area() abstract method in each of these two subclass Include any accessor methods (i.e. “get” methods) needed and a toString() method in each subclass.

3. Control classes contain a main method. Write a test control class that tests these classes by setting up an array of shapes and initializing each element of the array to a different shape, either a circle or a square. Then print out the details of each shape, including its class (see getClass() method at Object level) and the area of the shape.

Answer 1

Here is the completed code for this problem. Comments are included, go through it, learn how things work and let me know if you have any doubts or if you need anything to change. If you are satisfied with the solution, please rate the answer. Thanks

Note: if there is any extra features needed for Shape class or its sub classes, just let me know. I have written this based on the specifications mentioned in this question only.

// Shape.java

public abstract class Shape {

              /**

              * abstract method to calculate and return the area of the shape

              */

              public abstract double area();

}

// Square.java

public class Square extends Shape {

              private double side;

              // default constructor

              public Square() {

                           side = 0;

              }

              /**

              * @param side

              *            representing length of one side

              */

              public Square(double side) {

                           this.side = side;

              }

              // getters and setters

              public double getSide() {

                           return side;

              }

              public void setSide(double side) {

                           this.side = side;

              }

              @Override

              public double area() {

                           //area of square: side^2

                           return side * side;

              }

              @Override

              public String toString() {

                           //returning a string containing class name, side and area

                           return getClass().getSimpleName() + " [side: " + side + ", area: "

                                                       + area() + "]";

              }

}

// Circle.java

public class Circle extends Shape {

              private double radius;

              // default constructor

              public Circle() {

                           radius = 0;

              }

              /**

              * constructor taking value for radius

              * @param radius

              *            radius of the circle

              */

              public Circle(double radius) {

                           this.radius = radius;

              }

             

              //getters and setters

              public double getRadius() {

                           return radius;

              }

              public void setRadius(double radius) {

                           this.radius = radius;

              }

              @Override

              public double area() {

                           //area of circle=Pi*r^2

                           return Math.PI*radius*radius;

              }

             

              @Override

              public String toString() {

                           //returning a string containing class name, radius and area

                           return getClass().getSimpleName() + " [radius: " + radius+ ", area: "

                           + area() + "]";

              }

}

// Test.java

public class Test {

              public static void main(String[] args) {

                           // creating an array of 4 shapes

                           Shape shapes[] = new Shape[4];

                           // creating a square using default constructor, assigning to first

                           // location

                           shapes[0] = new Square();

                           // creating a square with side=12

                           shapes[1] = new Square(12);

                           // creating a circle using default constructor

                           shapes[2] = new Circle();

                           // creating a circle with radius=15

                           shapes[3] = new Circle(15);

                           // looping through the array and printing shapes, which will call the

                           // toString() methods of each object to print its class name,

                           // attribute(s) and area

                           for (int i = 0; i < shapes.length; i++) {

                                         System.out.println(shapes[i]);

                           }

              }

}

/*OUTPUT*/

Square [side: 0.0, area: 0.0]

Square [side: 12.0, area: 144.0]

Circle [radius: 0.0, area: 0.0]

Circle [radius: 15.0, area: 706.8583470577034]