how to make a constructor object in class object can be applied to given types?

Question

1. Write a class with the name Circle. The class needs one field (instance variable) with name radius of type double.

The class needs to have one constructor with parameter radius of type double and it needs to initialize the fields.

In case the radius parameter is less than 0 it needs to set the radius field value to 0.

Write the following methods (instance methods):

• Method named getRadius without any parameters, it needs to return the value of radius field.
• Method named getArea without any parameters, it needs to return the calculated area (radius * radius * PI). For PI use Math.PI constant.

2. Write a class with the name Cylinder that extends Circle class. The class needs one field (instance variable) with name height of type double.

The class needs to have one constructor with two parameters radius and height both of type double. It needs to call parent constructor and initialize a height field.

In case the height parameter is less than 0 it needs to set the height field value to 0.

Write the following methods (instance methods):

• Method named getHeight without any parameters, it needs to return the value of height field.
• Method named getVolume without any parameters, it needs to return the calculated volume. To calculate volume multiply the area with height.

TEST EXAMPLE

→ TEST CODE:

Circle circle = new Circle(3.75);
System.out.println("circle.radius= " + circle.getRadius());
System.out.println("circle.area= " + circle.getArea());
Cylinder cylinder = new Cylinder(5.55, 7.25);
System.out.println("cylinder.radius= " + cylinder.getRadius());
System.out.println("cylinder.height= " + cylinder.getHeight());
System.out.println("cylinder.area= " + cylinder.getArea());
System.out.println("cylinder.volume= " + cylinder.getVolume());

→ OUTPUT

circle.radius= 3.75
circle.area= 44.178646691106465
cylinder.radius= 5.55
cylinder.height= 7.25
cylinder.area= 96.76890771219959
cylinder.volume= 701.574580913447

NOTE: All methods should be defined as public NOT public static.

NOTE: In total, you have to write 2 classes.

NOTE: Do not add a main method to the solution code.

this is my Circle class

public class Circle {
    private double radius;

    public Circle(double radius) {
        this.radius = radius;
    }

    public double getRadius() {
        if(radius < 0){
            radius = 0;
            return radius;
        }else{
            return radius;
        }
    }

    public double getArea(){
        double area = (radius * radius * Math.PI);
        return area;
    }
}

this is my Cylinder Class

public class Cylinder extends Circle{
    private double height;

    public Cylinder(double radius, double height) {
        super(radius);
        this.height = height;
    }

    public double getHeight() {
        if(height > 0){
            return height;
        }else{
            height = 0;
            return height;
        }
    }

    public double getVolume(){
        double area = getArea() * getHeight();
        return area;
    }
}

But the question said that constructor object in class object cannot be applied to given types and that super(radius) required no arguments. and I also get an error at the double area = getArea() * getHeight(); that said cannot find symbol. can anyone help me with this problem ?

Answer 1

private double radius;

public Circle(double radius) {
    if (radius < 0) {
        this.radius = 0;
    } else {
        this.radius = radius;
    }

}

public double getRadius() {
    return radius;
}

public double getArea() {

    return this.radius * this.radius * Math.PI;

}

The Cylinder class: public class Cylinder extends Circle { private double height;

public Cylinder(double radius, double height) {
    super(radius);
    if (height < 0) {
        this.height = 0;
    } else {
        this.height = height;
    }

}

public double getHeight() {
    return height;
}

public double getVolume() {
    return getArea() * this.height;
}

}

!!!But it's important to put Cylinder EXTENDS Circle on Udemy course, for right compile...