Optimize generated range checks

Profiling cbench I have encountered performance overhead when constructing FlowCookie class – 20528ms for 105187 invocations. Of that, 15894ms was spent in Range.closed() invocations.

Looking at the generated code:

public FlowCookie(BigInteger _value) {
if (_value != null) {
boolean isValidRange = false;
List<Range<BigInteger>> rangeConstraints = new ArrayList<>();
rangeConstraints.add(Range.closed(new BigInteger("0"), new BigInteger("18446744073709551615")));
for (Range<BigInteger> r : rangeConstraints) {
if (r.contains(_value))

{ isValidRange = true; }

}
if (!isValidRange)

{ throw new IllegalArgumentException(String.format("Invalid range: %s, expected: %s.", _value, rangeConstraints)); }

}
this._value = _value;
}

It is rather obvious we can do better:

1) those range constraints should be lazily generated, but retained as static fields (double-checked loading)

2) BigInteger("0") should be replaced with BigInteger.ZERO (also ONE and TEN)

3) For values less that Long.MAX_VALUE, we should use BigInteger.valueOf(long)

4) rangeConstraints should end up being an ImmutableList