# double behaviour

Sethu Prem
Greenhorn
Posts: 6
Hi ,

Can somebody explain why double is being treated differently in the following code piece ?
double d1= 33.30+33.40+33.30;
double d2= 33.40+33.30+33.30;
double d3= 33.30+33.30+33.40;
Among these only d3 gives me result of 100.0 other 2 gives me 99.9.

Seth

Jean-Sebastien Abella
Ranch Hand
Posts: 60
This is a very old problem with floating point. If you want exact value you must use BigDecimal.

This is due to a limitation in the value you can represent on a bit pattern as there is an infinite number of decimal value between 0 and 1 there is a need for some imprecision.

Paul Santa Maria
Ranch Hand
Posts: 236
Jean-Sebastien is, of course, absolutely right. The key two points are:

1. Floating point math is an *approximation* (integer and BigDecimal is
*exact*)
... and ...
2. The order you perform the individual calculations affects what
values the intermediate results round to, which in turn affects the
final result.

EXAMPLE:

Sethu Prem
Greenhorn
Posts: 6
Thanks to both of you !!