Changed return type to List<Pair<Character, Integer>>. Pair is from Apache Commons Lang.

Sorry for late response and those mistakes. I fixed the fixed tests and shuffle method.

Changed getRandomDouble() to generate less NORMALIZED and more other types.

I did use enum at first but it kept failing to detect class name so I used class instead.
While keep trying to use enum in Preloaded, I noticed that the file name of Preloaded is determined by class keyword so I found a workaround by putting class FloatTypeEnum in a comment and declaring FloatTypeEnum as enum.

It is my bad. When I tried -Double.NaN like JavaScript, the sign remained unchanged so I thought it was unobtainable and provided an extra method to produce it. I assumed the same for POSITIVE_SIGNALING_NAN and NEGATIVE_SIGNALING_NAN as I could not find those in JavaScript and I did not know how to obtain them instead of converting from binary string.
I found that Double.longBitsToDouble(long) can be used to produce those values so I removed the said method.