Question

This is mine code, not fully finished, and sorry for Polish language but it’s easy to get it.
http://pastebin.com/QPmVaPFv
So, this is about vet, 4 variables are for price per visitor:
1. Big dog
2. Medium dog
3. Small dog
4.cat
After that next 4 variables are for numbers of visitor, same as before (big,medium,small,cat etc.)

Then text says:
every 5th big dog owner got 10% discount
every 3rd medium owner got 50% discount
every 4th cat owner got price at 1$ i.e

double zdpies=ldpies/5.;
double zspies=lspies/3.;
double zkot=ckot/4.;

This is that part with discounts

after that i made variables with calculations on discounted price

double cdpiespromo=cdpies/10.; Big dog
double cspiespromo=cspies/50.; medium dog
double ckotpromo=1; Cat

Then i made calculation for final price i.e for normal price without discount

— cena normalna: 21.6 x 51.0 = 1101.6000000000001

Process completed.

And i got that strange numbers, 51. is ok but 21.6 is wrong that must be 22 not 21.6. When i use “int” it says there is “loss of precision”, any ideas how to fix that ?

Here are last variables for calculating final price discounted and without discount.

double idp=ldpies-zdpies; this calculates numbers of visitors without discount
double idc=idp*cdpies; this calculates price number of visitor * normalpriceofbigdog.

Answer 1

There’s a great article on using float, double, BigDecimal etc for doing calculation here http://firstclassthoughts.co.uk/java/traps/java_double_traps.html

Bottom line is that there is no perfect solution.