Maybe. Java is quite fast, but for very different reasons than APL; I don't think it would transfer that easily. Part of the reason APLs are so fast is because the interpreter and all the code fit in cache; my copy of k is 76kb. I don't think there's a chance you could get that with the jvm. APL also relies heavily on SIMD, and I don't know how well-supported that is on the JVM.