(def str-number "42")

;; the first method: parse-long returns nil on bad input
(def number (parse-long str-number))

;; the second method: Java interop, throws on bad input
(def number2 (Long/parseLong str-number))

(println "number is" number)
(println "number2 is" number2)
(println "bad input is" (parse-long "42 apples"))