Question

Instructions

Write a Circle class (Circle.java) that has the following fields:

- radius (double)

- PI (final double initialized to 3.1415) // no need to have setters or getters for this

Include the following methods:

- Constructor (accepts radius of circle as an argument)

- Constructor (no argument that sets radius to 0.0)

- setRadius (set method for radius field)

- getRadius (get method for radius field)

- calcArea (calculates and returns area of circle: area = PI * radius * radius)

- calcDiameter (calculates and returns diameter of circle: diameter = radius * 2)

- calcCircumference (calculates and returns circumference of circle: circumference = 2* PI * radius)

Write a test program (TestCircle.java) that will ask user for the radius, creates the circle object, and then displays the area, diameter, and circumference.

Make sure to create 2 circle object instances - one with the radius as an argument, one without but sets the radius with the setRadius() method.

Thank you so much for your help!!

Answer 1

// Screenshot of the code & output

// Code to copy

Circle.java

public class Circle {
  
   private double radius;
   final double PI = 3.1415;
  
   // default-constructor
   public Circle ()
   {
       this.radius=0.0;  
   }
  
   //argument-constructor
   public Circle (double r)
   {
       this.radius=r;  
   }

   public double getRadius()
   {
       return radius;
   }
  
   public void setRadius(double radius)
   {
       this.radius = radius;
   }
   // calcArea method to calculate Circle Area
   public double calcArea() {
       double area = PI * radius * radius;
       return area;
   }
   // calcDiameter method to calculate Circle Diameter
   public double calcDiameter() {
       double diameter = radius * 2;
       return diameter;
   }
   // calcCircumference method to calculate Circle Circumference
   public double calcCircumference() {
       double circumference = 2* PI * radius;
       return circumference;
   }
}

TestCircle.java

import java.util.Scanner;
import java.text.DecimalFormat;
public class TestCircle {

   public static void main(String[] args) {
       DecimalFormat df = new DecimalFormat("0.00");
       double radius;
       Scanner input=new Scanner(System.in);      
System.out.print("Enter radius of circle :");
radius=input.nextDouble();
// circle object with out radius
Circle c1=new Circle ();
c1.setRadius(5);
System.out.println("\nCircle-1 object with out radius ");
System.out.println(df.format(c1.calcArea()));
System.out.println(df.format(c1.calcDiameter()));
System.out.println(df.format(c1.calcCircumference()));
  
// circle object with radius
       Circle c2=new Circle (radius);
       System.out.println("\nCircle-2 object with radius ");
System.out.println(df.format(c2.calcArea()));
System.out.println(df.format(c2.calcDiameter()));
System.out.println(df.format(c2.calcCircumference()));
// closing scanner object
input.close();
  
   }

}