// Create an abstract class.

// A class for two-dimensional objects.

abstract class TwoDShape {

private double width; // these are

private double height; // now private

private String name;

// A default constructor.

TwoDShape() {

width = height = 0.0;

name = "null";

}

// Parameterized constructor.

TwoDShape(double w, double h, String n) {

width = w;

height = h;

name = n;

}

// Construct object with equal width and height.

TwoDShape(double x, String n) {

width = height = x;

name = n;

}

// Construct an object from an object.

TwoDShape(TwoDShape ob) {

width = ob.width;

height = ob.height;

name = ob.name;

}

// Accessor methods for width and height.

double getWidth() { return width; }

double getHeight() { return height; }

void setWidth(double w) { width = w; }

void setHeight(double h) { height = h; }

String getName() { return name; }

void showDim() {

System.out.println("Width and height are " + width + " and " + height);

}

// Now, area() is abstract.

abstract double area();

}

// A subclass of TwoDShape for triangles.

class Triangle extends TwoDShape {

private String style;

// A default constructor.

Triangle() {

super();

style = "null";

}

//Constructor

Triangle(String s, double w, double h) {

super(w, h, "triangle"); // call superclass constructor

style = s;

}

// Construct an isoceles triangle.

Triangle(double x) {

super(x, "triangle"); // call superclass constructor

style = "isosceles";

}

// Construct an object from an object.

Triangle(Triangle ob) {

super(ob); // pass object to TwoDShape constructor

style = ob.style;

}

// Override area() for Triangle.

double area () {

return getWidth() * getHeight() / 2;

}

void showStyle() {

System.out.println("Triangle is " + style);

}

}

// A subclass of TwoDShape for rectangles.

class Rectangle extends TwoDShape {

// A default constructor.

Rectangle() {

super();

}

// Constructor for Rectangle.

Rectangle(double w, double h) {

super(w, h, "rectangle"); // call superclass constructor

}

// Construct a square.

Rectangle(double x) {

super(x, "rectangle"); // call superclass constructor

}

// Construct an object from an object.

Rectangle(Rectangle ob) {

super(ob); // pass object to TwoDShape constructor

}

boolean isSquare() {

if(getWidth() == getHeight()) return true;

return false;

}

// Override area() for Rectangle.

double area() {

return getWidth() * getHeight();

}

}

class AbsShape {

public static void main(String args[]) {

TwoDShape shapes[] = new TwoDShape[4];

shapes[0] = new Triangle("right", 8.0, 12.0);

shapes[1] = new Rectangle(10);

shapes[2] = new Rectangle(10, 4);

shapes[3] = new Triangle(7.0);

for(int i=0; i < shapes.length; i++) {

System.out.println("object is " + shapes[i].getName());

System.out.println("Area is " + shapes[i].area());

System.out.println();

}

}

}