Can we declare a constructor inside a method in java?

You can only create a constructor with in a class whose name is same as the class name, you cannot definre it inside a method. 

Y to add constructor. According to java when you declare a function or method, a constructor is automatically derived. So if u try to add it would be overloaded.

it shows error. So its not possible.

No, it is not possible.

Yes you can create it if you have an inner class inside your method.

Yes u can create