How can I tell if a decimal number represented as a String will fit in a double?

Question

I'm parsing a String value which I know contains a number.

If it only contains digits and it's between Integer.MIN_VALUE and Integer.MAX_VALUE I'm parsing it as an int, similarly for long otherwise I'm using BigInteger.

If it contains a decimal value I'd either like to parse it as a double or as a BigDecimal.

Can I test if the numeric value in the String "fits" into a double and is therefore safe to parse as a double, or whether it needs to be held in a BigDecimal to prevent loss of precision?

Answer 1

and is therefore safe to parse as a double, or whether it needs to be held in a BigDecimal to prevent loss of precision?

This won't be the answer that you're looking for, but since you seem to be concerned about loss of precision, you should use a BigDecimal in place of any double.

The number 0.1 can fit in a double, but it isn't precise (as 0.1 can not be represented accurately in binary).

See: Is floating point math broken?