In reply to rakesh reddy:
Your problem arises from not having a default value for ‘in’ in the new() function of your base class. When a default value for an argument isn’t provided, it becomes a mandatory argument.
The extended class will call super.new() for the base class during as part of the implicit new() function. Since the implicit call to super.new() has no argument, you get this error.
You can fix it by providing a default value for ‘in’ in the base class, or defining the new() function in the extended class and calling super.new() with an argument.