Java Programs[Important]

1.  
2.   WRITE A JAVA PROGRAM to create an abstract class named Shape, that contains an empty method named numberOfSides(). Provide three classes named Trapezoid, Triangle and Hexagon, such that each one of the classes contains only the method numberOfSides(), that contains the number of sides in the given geometrical figure.
3.  
4. Program :
5.  
6. abstract class Shape
7.  { 
8. abstract void numberOfSides();
9.  } 
10. class Trapezoid extends Shape
11. {
12. 
    
13. void numberOfSides()
14.  {
15.  System.out.println(" Trapezoidal has four sides");
16.  } 
17. } 
18. class Triangle extends Shape
19.  { 
20. void numberOfSides()
21.  { 
22. System.out.println("Triangle has three sides"); 
23. }
24.  }
25.  class Hexagon extends Shape 
26. { 
27. void numberOfSides()
28.  { 
29. System.out.println("Hexagon has six sides");
30.  }
31.  }
32.  class ShapeDemo 
33. { 
34. public static void main(String args[ ])
35.  { 
36. Trapezoid t=new Trapezoid(); 
37. Triangle r=new Triangle();
38.  Hexagon h=new Hexagon(); 
39. Shape s;
40. 
    
41. s=t; 
42. s.numberOfSides();
43.  s=r;
44.  s.numberOfSides();
45.  s=h; 
46. s.numberOfSides();
47.  }
48.  }