double?

;;;; true for instances of java.lang.Double

(double? 1.0)
;;=> true
(double? (new Double "1"))
;;=> true

;;;; false for instances of java.lang.Float, java.lang.BigDecimal

(double? (new Float "1"))
;;=> false
(double? 1.0M)
;;=> false
(double? (new BigDecimal "1"))
;;=> false