(vii)John was asked to write a Java code to calculate the surface area of a cone. The following code was written by him:
Formula:
Surface area of a cone is A = πrℓ, where ℓ = √(r² + h²)

class area
{
double area(double r, double h)
{
double l, a;
a = 22.0/7 * r * l;
l = Math.sqrt(r * r + h * h);
return a;
}
}

Task:
(a) Specify the type of error in the above program.(b) Correct the program and write the error-free version.

Question

(vii)John was asked to write a Java code to calculate the surface area of a cone. The following code was written by him:
Formula:
Surface area of a cone is A = &pi;rℓ, where ℓ = &radic;(r&sup2; + h&sup2;)


class area  
{  
    double area(double r, double h)  
    {  
        double l, a;  
        a = 22.0/7 * r * l;  
        l = Math.sqrt(r * r + h * h);  
        return a;  
    }  
}  


Task:
(a) Specify the type of error in the above program.(b) Correct the program and write the error-free version.

Accepted Answer

Solution:
(a) Type of Error:
The error in the program is the incorrect order of operations. The variable l is used before it is initialized, which leads to an undefined variable error or logical error.


variable l might not have been initialized
        a = 22.0/7 * r * l;
                         ^
1 error


(b) Corrected Program:
Below is the corrected version of the program:


class Area  
{  
    double area(double r, double h)  
    {  
        double l, a;  
        l = Math.sqrt(r * r + h * h); // Compute l first  
        a = (22.0 / 7) * r * l; // Use l after initialization  
        return a;  
    }  

    public static void main(String args[])  
    {  
        Area obj = new Area();  
        double result = obj.area(5, 12); // Example values (r = 5, h = 12)  
        System.out.println("Surface Area of Cone: " + result);  
    }  
}  




Explanation of Fixes:

 
Fixed the order of operations:

 
l = Math.sqrt(r * r + h * h); is now calculated before using it in a = (22.0 / 7) * r * l;.



 
Added a main method:

 
This allows the program to run and test the output.




Expected Output for r = 5, h = 12:


Surface Area of Cone: 94.28571428571429

(vii)
John was asked to write a Java code to calculate the surface area of a cone. The following code was written by him:

Formula:

Task:

Answer with Explanation

Solution:

(a) Type of Error:

(b) Corrected Program:

Explanation of Fixes:

Expected Output for r = 5, h = 12: