About this question
To learn more about OOP, @nhgrif challenged me to implement a Shape abstract class (more details in code remarks below. Here is how I did it. Any and all advice appreciated!
Shape.java
/* nhgrif says:
* Phrancis ready for inheritance/polymorphism?
* Given the following abstract class:
*
* public abstract class Shape {
* public abstract double area();
* public abstract double perimeter();
* }
*
* Implement a Circle, Triangle, and Rectangle class which extend the class Shape.
* Ex: public class Circle extends Shape ... etc
*/
public abstract class Shape {
public abstract double area();
public abstract double perimeter();
}
Rectangle.java
public class Rectangle extends Shape {
private final double width, length; //sides
public Rectangle() {
this(1,1);
}
public Rectangle(double width, double length) {
this.width = width;
this.length = length;
}
@Override
public double area() {
// A = w * l
return width * length;
}
@Override
public double perimeter() {
// P = 2(w + l)
return 2 * (width + length);
}
}
Circle.java
public class Circle extends Shape {
private final double radius;
final double pi = Math.PI;
public Circle() {
this(1);
}
public Circle(double radius) {
this.radius = radius;
}
@Override
public double area() {
// A = π r^2
return pi * Math.pow(radius, 2);
}
public double perimeter() {
// P = 2πr
return 2 * pi * radius;
}
}
Triangle.java
public class Triangle extends Shape {
private final double a, b, c; // sides
public Triangle() {
this(1,1,1);
}
public Triangle(double a, double b, double c) {
this.a = a;
this.b = b;
this.c = c;
}
@Override
public double area() {
// Heron's formula:
// A = SquareRoot(s * (s - a) * (s - b) * (s - c))
// where s = (a + b + c) / 2, or 1/2 of the perimeter of the triangle
double s = (a + b + c) / 2;
return Math.sqrt(s * (s - a) * (s - b) * (s - c));
}
@Override
public double perimeter() {
// P = a + b + c
return a + b + c;
}
}
And this is what I used to test it all, which it all works as intended:
TestShape.java
public class TestShape {
public static void main(String[] args) {
// Rectangle test
double width = 5, length = 7;
Shape rectangle = new Rectangle(width, length);
System.out.println("Rectangle width: " + width + " and length: " + length
+ "nResulting area: " + rectangle.area()
+ "nResulting perimeter: " + rectangle.perimeter() + "n");
// Circle test
double radius = 5;
Shape circle = new Circle(radius);
System.out.println("Circle radius: " + radius
+ "nResulting Area: " + circle.area()
+ "nResulting Perimeter: " + circle.perimeter() + "n");
// Triangle test
double a = 5, b = 3, c = 4;
Shape triangle = new Triangle(a,b,c);
System.out.println("Triangle sides lengths: " + a + ", " + b + ", " + c
+ "nResulting Area: " + triangle.area()
+ "nResulting Perimeter: " + triangle.perimeter() + "n");
}
}
