Question: You are to design a Java application to carry out additions and subtractions for numbers of any length.

A number is represented as an object which includes a sign and two strings for the whole and decimal parts of the number. And, the operations must be done by adding or subtracting characters directly. You are not allowed to convert these strings to numbers before the operation.

The program must use a "Number" class which includes at least the following methods:

Number ( );
Number (double n);
Number add (Number RHS);
Number subtract (Number RHS);
String toString ( );

Make this application using java programming. Create this application in simple way.