Java 7 introduced the ability to use a digit separator (``++_++``) to split a literal number into groups of digits for better readability.


To ensure that readability is really improved by using digit separators, this rule verifies:


* *Homogeneity*
**   Except for the left-most group, which can be smaller, all groups in a number should contain the same number of digits. Mixing group sizes is at best confusing for maintainers, and at worst a typographical error that is potentially a bug.

* *Standardization*
**  It is also confusing to regroup digits using a size that is not standard. This rule enforce the following standards:
*** Decimal numbers should be separated using groups of 3 digits.
*** Hexadecimal numbers should be separated using groups of 2 or 4 digits.
*** Octal and Binary should be separated using groups of 2, 3 or 4 digits.

Furthermore, using groups with more than 4 consecutive digits is not allowed because they are difficult for maintainers to read.