In spec there is written:

Enum Constant Summary
*AFTER*
          Indicates that entries with a value after the supplied value should be included.
*BEFORE*
          Indicates that entries with a value before the supplied value should be included.
EQUAL
          Indicates that entries with a value equal to the supplied value should be included.
NOT_EQUAL
          Indicates that entries with a value not equal to the supplied value should be included.

public static final RowFilter.ComparisonType[] values()
    Returns an array containing the constants of this enum type, *in the order they're declared.*

But values are returned in the following order:
*BEFORE*
*AFTER*
EQUAL
NOT_EQUAL