AverageLong: simplify (do not use BigInteger, compute the result dire…

…ctly)

Multiplying double by 0x1.0p64 simply updates the exponent, so this should not produce any precision problems.

src/main/java/one/util/streamex/Internals.java

@@ -835,12 +835,7 @@ public AverageLong combine(AverageLong other) {
  public OptionalDouble result() {
  if (cnt == 0)
  return OptionalDouble.empty();
- if (hi == 0 && lo >= 0 || hi == -1 && lo < 0) {
- return OptionalDouble.of(((double) lo) / cnt);
- }
- return OptionalDouble.of(new BigDecimal(new BigInteger(java.nio.ByteBuffer.allocate(16).order(
- ByteOrder.BIG_ENDIAN).putLong(hi).putLong(lo).array())).divide(BigDecimal.valueOf(cnt),
- MathContext.DECIMAL64).doubleValue());
+ return OptionalDouble.of(((double) (hi + (lo < 0 ? 1 : 0)) / cnt) * 0x1.0p64 + ((double) lo) / cnt);
  }
  }