How do I quickly calculate a large positive, or negative, power of 2 in Java?

Question

I want to calculate powers of two larger than 2⁶², so I must store the result in a double and can't use the (1L << exp) trick. I also want to store fractions representing negative powers of two.

Answer 1

Java provides java.lang.Math.scalb(float f, int scaleFactor) for this. It multiplies f by 2^scaleFactor.