String Calculator

A kata from Roy Osherove

1. First step

Create a StringCalculator class with a method

int add(String number)

• The method can take 0,1 or 2 numbers separated by comma and return their sum,

• "" should return 0

• "1" should return 1

• "1,2,3" should return 6

2. Allow the add method to handle an unknown number of arguments

• "1\n2" should return 3.
• "1\n2,3" should return 6.

3. Allow the add method to handle a different delimiter

To change the delimiter, the beginning of the string will contain a separate line that looks like this :

"//[delimiter]\n[numbers]

Example :

"//;\n1;2"   => 3
"//|\n1|2|3" => 6

All existing scenarios should work as before.

4. Negatives numbers

Calling add with negatives numbers will throw an exception "Negative not allowed : " listing all negative numbers that were in the list of numbers

"-1,2"    => Negative not allowed : -1
"2,-4,-6" => Negative not allowed : -4,-6

5. Big numbers

Numbers over 1000 are silently ignored.

6. Others operations

Write a function for multiply with same rules