why we use polymorphism in java code example

Example: polymorphism in java

// Polymorphism in java example
class Shapes
{
   public void sides()
   {
      System.out.println("sides() method.");
   }
}
class Square extends Shapes
{
   public void sides()
   {
      System.out.println("square has four sides.");
   }
}
class Triangle extends Shapes
{
   public void sides()
   {
      System.out.println("triangle has three sides.");
   }
}
class PolymorphismExample
{
   public static void main(String[] args)
   {
      Shapes shape = new Shapes();
      Shapes square = new Square();
      Shapes triangle = new Triangle();
      shape.sides();
      square.sides();
      triangle.sides();
   }
}