Write a command line program, SOD, in Java that computes the sum of digits for a single integer argument > 0, subject to the following:

1. The program must check for a correct argument.

2. It must print out according to the examples below.

3. It must include a method, doSOD(int i), that computes the sum of digits recursively.

Examples:

java SOD

Error: argument is missing.

java SOD 0

Error: 0 is an invalid argument.

java SOD 1234

Sum of digits of 1234 is 10.