In This post, i describe some inheritance related program. Inheritance is also known as parent-child relationship or IS-A relationship. Protected member of the super class acts as a public member in the child class. All super class constructor is call before executing the child class constructor and super keyword is used to access the super class version of methods and veriables.

Write an inheritance hierarchy for classes Quadrilateral, Trapezoid, Parallelogram, Rectangle and Square. Use Quadrilateral as the super class of the hierarchy. The instance variables of Quadrilateral should be the x-y coordinate pairs for the four endpoints of the Quadrilateral. Write a program that instantiates objects of your classes and outputs each object's area (except Quadrilateral).

public class Quadrilateral
{
protected int x1,x2,x3,x4,y1,y2,y3,y4;
protected void setCoordinate(int a,int b,int c,int d,int e,int f,int g,int h)
{
x1=a;
y1=b;
x2=c;
y2=d;
x3=e;
y3=f;
x4=g;
y4=h;
}
}

public class Square extends Quadrilateral
{
Square(int a,int b,int c,int d,int e,int f,int g,int h)
{
setCoordinate(a,b,c,d,e,f,g,h);
}
int area()
{
int d=(int)Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
return d*d;
}
}

public class Rectangle extends Quadrilateral
{
Rectangle(int a,int b,int c,int d,int e,int f,int g,int h)
{
setCoordinate(a,b,c,d,e,f,g,h);
}
int area()
{
int d1=(int)Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
int d2=(int)Math.sqrt((x1-x4)*(x1-x4)+(y1-y4)*(y1-y4));
return d1*d2;
}
}

public class Trapezoid extends Quadrilateral
{
private int height;
Trapezoid(int a,int b,int c,int d,int e,int f,int g,int h,int height)
{
setCoordinate(a,b,c,d,e,f,g,h);
this.height=height;
}
int area()
{
int d1=(int)Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
int d2=(int)Math.sqrt((x3-x4)*(x3-x4)+(y3-y4)*(y3-y4));
return (int)((d1+d2)*height)/2;
}
}

public class Parallelogram extends Quadrilateral
{
private int height;
Parallelogram(int a,int b,int c,int d,int e,int f,int g,int h,int height)
{
setCoordinate(a,b,c,d,e,f,g,h);
this.height=height;
}
int area()
{
int d1=(int)Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
return d1*height;
}
}

public class TestQuadrilateral
{
public static void main(String []args)
{
Square sq=new Square(10,10,20,10,20,20,10,20);
System.out.println("Area Of The Square is " + sq.area());
Rectangle rec=new Rectangle(10,10,30,10,30,20,10,20);
System.out.println("Area Of The Rectangle is " + rec.area());
Parallelogram p=new Parallelogram(10,10,30,10,20,20,0,20,8);
System.out.println("Area Of The Parallelogram is " + p.area());
Trapezoid t=new Trapezoid(10,10,30,10,40,20,0,20,8);
System.out.println("Area Of The Trapezoid is " + t.area());
}
}

Output:

Area Of The Square is 100
Area Of The Rectangle is 200
Area Of The Parallelogram is 160
Area Of The Trapezoid is 240