Question

I need to convert 0.5 in base 10 to base 2 (0.1). I have tried using

Double.doubleToRawLongBits(0.5) 

and it returns 4602678819172646912 which I guess is in hex, but it does not make sense to me.

Answer 1

Multiply you number by 2^n, convert to an BigInteger, convert to binary String, add a decimal point at position n (from right to left).

Example (quick & ++dirty):

private static String convert(double number) {     int n = 10;  // constant?     BigDecimal bd = new BigDecimal(number);     BigDecimal mult = new BigDecimal(2).pow(n);     bd = bd.multiply(mult);     BigInteger bi = bd.toBigInteger();     StringBuilder str = new StringBuilder(bi.toString(2));     while (str.length() < n+1) {  // +1 for leading zero         str.insert(0, '0');     }     str.insert(str.length()-n, '.');     return str.toString(); }