programming forums Java Mobile Certification Databases Caching Books Engineering Micro Controllers OS Languages Paradigms IDEs Build Tools Frameworks Application Servers Open Source This Site Careers Other Pie Elite all forums
this forum made possible by our volunteer staff, including ...
Marshals:
• Campbell Ritchie
• Jeanne Boyarsky
• Ron McLeod
• Paul Clapham
• Liutauras Vilda
Sheriffs:
• paul wheaton
• Rob Spoor
• Devaka Cooray
Saloon Keepers:
• Stephan van Hulst
• Tim Holloway
• Carey Brown
• Frits Walraven
• Tim Moores
Bartenders:
• Mikalai Zaikin

# Floating Confusion

Greenhorn
Posts: 22
• Number of slices to send:
Optional 'thank-you' note:
Hi All,

I have a confusion...

The following code snippet prints "true"

float f = 1.0F/3.0F;
System.out.println( (f * 3.0F) == 1.0F );

whereas the following prints "false"

double d = 1.0F/3.0F;
System.out.println( (d * 3.0F) == 1.0F );

How is it possible, the value of 1/3 cannot be precisely stored by either variable type. Then why does double return false?

Am I missing something?

Thanks!

Ranch Hand
Posts: 2412
• Number of slices to send:
Optional 'thank-you' note:
Remember that an implict conversion to double is taking place.

Consider this code.

The output is

Talib Jockey
Greenhorn
Posts: 22
• Number of slices to send:
Optional 'thank-you' note:
Thanks bro..but its kindda wierd!!

Ranch Hand
Posts: 1970
1
• Number of slices to send:
Optional 'thank-you' note:
(Not an Advanced question at all)

Testing for equality, with floating point, is almost always wrong. It is an inexact data type, so exact equality test generally does not do what you want.

Therefore you have two mistakes: -
• using float constants (F suffix) with double type
• worrying about exact equality tests in floating-point

• [ September 25, 2006: Message edited by: Peter Chase ]

 Everybody! Do the Funky Monkey! Like this tiny ad! a bit of art, as a gift, the permaculture playing cards https://gardener-gift.com