Question

Circle Class (This is in JAVA)

/**
 * Defines a basic shape with just area
 *
 * @author Jo Belle
 * @version 0.2 (10/05/2020)
 */
public class Shape{
    private double area;

    public Shape(){ area = 0.0; }
    public Shape( double a ){ this.area = a; }
    public void setArea( double a ){ area = a; }
    public double getArea(){ return area; }
    public String toString(){
        return "Shape:\n\tarea: " + area;
    }
}

/**
 * Create a simple Circle object
 *
 * @author Jo Belle
 * @version 0.2 (10/12/2020)
 */
public class ShapeDriver{
    public static void main( String[] args ){
        Circle cir = new Circle( );
        cir.setRadius( 5.0 );
        System.out.println( cir.toString() );
    }
}

Given the code above, write a Circle class (and save it in a file named Circle.java) that inherits from the Shape class. Include in your Circle class, a single private field double radius. Also include a method void setRadius(double r) (which also sets area) and a method double getRadius() (which also returns the current radius). Change the accessibility modifier for area in the Shape class to be more appropriate for a base class. Make sure that ShapeDriver's main() method executes and produces the following output:

Shape:
        area: 78.53981633974483
        radius: 5.0

Submit both your Circle.java and your Shape.java files.

Answer 1

Answer.

Shape.java

public class Shape{

private double area;

public Shape(){
area = 0.0;
}

public Shape( double a ){
this.area = a;
}

public void setArea( double a ){
area = a;
}

public double getArea(){
return area;
}

public String toString(){
return "Shape:\n\tarea: " + area;
}

}

Circle.java

public class Circle extends Shape{

//declaring private field
private double radius;

//getter method
public double getRadius() {
return radius;
}

//setter method
public void setRadius(double radius) {
this.radius = radius;
this.setArea(Math.PI*this.radius*this.radius); //sets area using method in Shape class
}

//This is to be overridden only if you want to display radius in output
public String toString() {
return super.toString()+"\n\tradius: "+radius;
}

}

ShapeDriver.java

public class ShapeDrive{

public static void main( String[] args ){
Circle cir = new Circle( );
cir.setRadius(5.0 );
System.out.println( cir.toString() );
}

}

Output

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Thank you.