CodingBat: Either24 (Java)

Given an array of ints, return true if the array contains a 2 next to a 2 or a 4 next to a 4, but not both.

either24([1, 2, 2]) → true
either24([4, 4, 1]) → true
either24([4, 4, 1, 2, 2]) → false