Reflection on Enums

One of the methods I am currently writing for my Java library takes an array of an arbitrary enumeration type as its sole argument. If any of these is non-null, I can access the instance of java.lang.Class representing that enumeration type, which may or may not be a public type. (If they are all null, there is no purpose to this anyway under the circumstances.) How do I get the number of possible values that enumeration type has? The approach I am currently using - Array.getLength(clazz.getMethod("values").invoke(null)); - fails when the Enum class is not public. How do I fix this?