README.md

Guava against Million dollar error

Let's use Google Guava Library to fight against the million dollar error.

As start point we have a simple sum function and we need it to validate the following, in order:

that parameters are not null
if first parameter is null throw NPE with message "Illegal Argument passed: First parameter is Null."
if second parameter is null throw NPE with message "Illegal Argument passed: Second parameter is Null."
that parameters are positive ( > 0 )
if this is not the case then throw IllegalArgumentException with message "Illegal Argument passed: Non-positive value d." where d is the non-positive value (no need to format the value, just turn it into a string). If both values are non-positive, use the first parameter.

Hint: you could use a reading to class com.google.common.base.Preconditions