I have the assignment to use an abstract class as a superclass "Shape". It has three classes that extend that class, Triangle, Circle, and Square. Each class is supposed to compute the area and the perimeter of these shapes. I have things working when I System.out.println(shapeArray[i].computeArea());
in a for loop. But when I try and call the toString method from the child classes in that for loop everything returns as "0". I appreciate anybody taking the time to help out, as I am pretty stuck here. I feel like I have read, and re-read threads, and my textbook all day. I feel like there is just some dumb mistake here that I cannot see.
Shape.java
public class Circle extends Shape {
private double radius;
final private double PI = 3.14159;
private double circumfrence;
private double area;
Circle(double radius) {
this.radius = radius;
}
@Override
public double computeArea() {
double radSquared = radius * radius;
double area = PI * radSquared;
return area;
}
@Override
public double computePerimeter() {
circumfrence = 2 * PI * radius;
return circumfrence;
}
@Override
public String toString() {
return "Area of Circle: " +area + "\nCircumfrence of Circle: " + circumfrence;
}
}
Triangle.java
public class Triangle extends Shape {
private double side1;
private double side2;
private double side3;
private double area;
private double perimeter;
Triangle (double side1, double side2, double side3) {
this.side1 = side1;
this.side2 = side2;
this.side3 = side3;
}
@Override
public double computeArea() {
double s =(side1 + side2 + side3) / 2;
double area= Math.sqrt(s * (s - side1) * (s - side2) * (s - side3));
area = this.area;
return area;
}
@Override
public double computePerimeter() {
perimeter = side1 + side2 + side3;
return perimeter;
}
@Override
public String toString() {
return "Area of Triangle: " + area+ "\nPerimeter of Triangle: " + perimeter;
}
}
Circle.java
public class Circle extends Shape {
private double radius;
final private double PI = 3.14159;
private double circumfrence;
private double area;
Circle(double radius) {
this.radius = radius;
}
@Override
public double computeArea() {
double radSquared = radius * radius;
double area = PI * radSquared;
return area;
}
@Override
public double computePerimeter() {
circumfrence = 2 * PI * radius;
return circumfrence;
}
@Override
public String toString() {
return "Area of Circle: " +area + "\nCircumfrence of Circle: " + circumfrence;
}
}
Rectangle.java
public class Rectangle extends Shape {
private double length;
private double height;
private double sumOfLength;
private double sumOfHeight;
private double area;
private double perimeter;
Rectangle(double length, double height) {
this.height = height;
this.length = length;
}
@Override
public double computeArea() {
area = (length * height);
return area;
}
@Override
public double computePerimeter() {
sumOfLength = length * 2;
sumOfHeight = height * 2;
perimeter = sumOfLength + sumOfHeight;
return perimeter;
}
@Override
public String toString() {
return "Area of Rectangle: " +area + "\nPerimeter of Rectangle: " + perimeter;
}
}
ShapeArray.java
public class ShapeArray {
public static void main(String [] args) {
Shape shapeArray[] = new Shape[3];
Circle circ = new Circle(9);
Rectangle rect = new Rectangle(10, 6);
Triangle tri = new Triangle(6, 8, 12);
shapeArray[0] = circ;
shapeArray[1] = rect;
shapeArray[2] = tri;
for (int i = 0; i <= 2; i++) {
System.out.println(shapeArray[i].toString());
}
}
}
Output:
Area of Circle: 0.0
Circumfrence of Circle: 0.0
Area of Rectangle: 0.0
Perimeter of Rectangle: 0.0
Area of Triangle: 0.0
Perimeter of Triangle: 0.0
your class Triangle.computeArea
method change the from area = this.area;
to this.area=area;
Other class like this.
In you must call in for loop shapeArray[i].computeArea()
and shapeArray[i].computePerimeter()
before shapeArray[i].toString()
.
In ShapeArray.java
//other code
for (int i = 0; i <= 2; i++) {
shapeArray[i].computeArea();
shapeArray[i].computePerimeter()
System.out.println(shapeArray[i].toString());
}
//other code
It prints 0 because you don't call calculation of perimeter and area for class instance before print it. But I also recommend reviewing your code that it does not use unnecessary variables.
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