Java. How to disable rounding in DecimalFormat

Question

Can I disable rounding "feature" in DecimalFormat?

For example:

DecimalFormat f = new DecimalFormat();

f.parseObject("123456789012345.99");

Result is 1.2345678901234598E14

java version "1.6.0_21"

Answer 1

This is nothing to do with a feature of Java. It is due to the limited precision of IEEE 64-bit double floating numbers. In fact all data types have limits to their precision. SOme are larger than others.

double d = 123456789012345.99;
System.out.println(d);

prints

1.2345678901234598E14

If you want more precision use BigDecimal.

BigDecimal bd = new BigDecimal("123456789012345.99");
System.out.println(bd);

prints

123456789012345.99

Even BigDecimal has limits too, but they are far beyond what you or just about any one else would need. (~ 2 billion digits)

EDIT: The largest known primes fit into BigDecimal http://primes.utm.edu/largest.html

Answer 2

No, that's not rounding, that's just the way floating point numbers work.

The only way to do what you want is to use BigDecimal.

I'd recommend that you read "What Every Computer Scientist Should Know About Floating Point Arithmetic".