Guava: CharMatcher.countIn should account for null sequence

[devikasondhi]

The documentation for the CharMatcher.countIn method does not state the expected behaviour if the input sequence is null. The user may expect the method to return 0 for such a case but the implementation throws NullPointerException (which could also be considered as a valid output). This ambiguity should be explicitly clarified in the documentation or else handled well in the code.

[perceptron8]

"Guava's utilities are designed to fail fast in the presence of null rather than allow nulls to be used, so long as there is a null-friendly workaround available" (wiki/UsingAndAvoidingNullExplained)

I would say that NPE is expected by default.

As for workaround, you can use Strings.nullToEmpty to normalize your string before passing it to CharMatcher.countIn.