(alength array)
Returns the length of the Java array. Works on arrays of all types.
user=> (def my-array (into-array Integer/TYPE [1 2 3]))
#'user/my-array
user=> (alength my-array)
3
2D simple array example
user=> (def a (to-array-2d [[1 2] [3 4 5] [1]]))
#'user/a
user=> (alength a)
3