How to accept an empty integer value?

Question

My program calculates the surface area of a cone (pi * radius * slant-height). I'm using an if-elseif ladder which says that if the slant-height is left empty and the vertical-height is entered, the program will calculate the slant-height via Pythagoras theorem. But I don't know how to make the program accept a null value

I tried using if(slant_height==null) but it says that the types are incompatible and == is a "bad operator type"

{
public void CSAcone(double radius,double slant_height,double height) {
    if (slant_height == null)
    {
         slant_height=Math.sqrt((radius*radius) + (height*height));
         double CSA=(22*radius*slant_height) / 7;

         System.out.println("radius= "+radius);
         System.out .println("height= "+slant_height);
         System.out .println("Curved Suface Area= "+CSA);
    }

    if(height == null) 
    {
        double CSA=(22*radius*slant_height) / 7;

        System.out.println("radius= " + radius);
        System.out.println("height= " + slant_height);
        System.out.println("Curved Suface Area= " + CSA);
    }
}}

As the method signature is written, slant_height will never be null, because you cannot call CSAcone by providing a null value for that variable, the code wouldn't compile. Notice slant_height is double, not Double. — lealceldeiro
– lealceldeiro, Commented May 18, 2019 at 8:44
Read this, stackoverflow.com/questions/8643276/object-vs-primitive — Burak Akyıldız
– Burak Akyıldız, Commented May 18, 2019 at 8:54

mohammadReza Abiri · Accepted Answer · 2019-05-18 08:55:35Z

1

try this :

 public void CSAcone(double radius, double slant_height, double height) {
    if (slant_height == 0.0f) {
        slant_height = Math.sqrt((radius * radius) + (height * height));
        double CSA = (22 * radius * slant_height) / 7;
        System.out.println("radius= " + radius);
        System.out.println("height= " + slant_height);
        System.out.println("Curved Suface Area= " + CSA);
    }
    if (height == 0.0f) {
        double CSA = (22 * radius * slant_height) / 7;
        System.out.println("radius= " + radius);
        System.out.println("height= " + slant_height);
        System.out.println("Curved Suface Area= " + CSA);
    }
}

answered May 18, 2019 at 8:55

mohammadReza Abiri

1,7991 gold badge12 silver badges20 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Screwdriver Over a year ago

I could have done that but it would mean that the user has to enter 0.0 in one of the boxes

Thuvarakan Tharmarajasingam · Accepted Answer · 2019-05-18 08:59:29Z

0

Change your variable types to the wrapper classes(Integer, Double) of primitive types(int, double). In Java, primitive types cannot be null.

answered May 18, 2019 at 8:59

Thuvarakan Tharmarajasingam

1,22510 silver badges13 bronze badges

Comments

coder21 · Accepted Answer · 2019-05-18 09:05:51Z

0

null can be cast to any reference type, but not to any primitive type such as int or boolean.

You can use primitive types and send a special value to specify emptyness.

Or just use object types (Integer, Boolean, Double etc.) and check null values(as you did).

public void CSAcone(Double radius,Double slant_height,Double height){
   if(radius == null){}
   if(slant_height == null){}
   if(height == null){}
   // ...
}

edited May 18, 2019 at 9:05

answered May 18, 2019 at 8:56

coder21

111 silver badge5 bronze badges

Collectives™ on Stack Overflow

How to accept an empty integer value?

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest