For one of my projects a high-precision FFT had to be programmed. So I started writing "BigMath", a Java™ class that provides some functions based on Java's arbitrary-precision BigInteger format (i.e. calculation of Pi, E, Factorial, Root, Ld, (a)Sine/(a)Cosine, (a)Tan, (i)FFT, format conversion, bit reversal, ...). You can download "BigMath" from the link below. If you need source code, please shoot me an e-mail.