This question involves the implementation of the AddtionPattern class, which generates a number pattern. The AdditionPattern object is constructed with two positive integer parameters, as described below. The first positive integer parameter indicates the starting number in the pattern.
The second positive integer parameter indicates the value that is to be added to obtain each subsequent number in the pattern.
The AdditionPattern class also supports the following methods.

currentNumber, which returns the current number in the pattern
next, which moves to the next number in the pattern
prev, which moves to the previous number in the pattern or takes no action if there is no previous number
The following table illustrates the behavior of an AdditionPattern object that is instantiated by the following statement.

AdditionPattern plus3 = new AdditionPattern(2, 3);

Write the complete AdditonPattern class. Your implementation must meet all specifications and conform to all examples.