• Post Reply Bookmark Topic Watch Topic
  • New Topic
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 all forums
this forum made possible by our volunteer staff, including ...
Marshals:
  • Campbell Ritchie
  • Paul Clapham
  • Ron McLeod
  • Bear Bibeault
  • Liutauras Vilda
Sheriffs:
  • Jeanne Boyarsky
  • Junilu Lacar
  • Henry Wong
Saloon Keepers:
  • Tim Moores
  • Stephan van Hulst
  • Jj Roberts
  • Tim Holloway
  • Piet Souris
Bartenders:
  • Himai Minh
  • Carey Brown
  • salvin francis

Please explain the concept of Float.Nan

 
Ranch Hand
Posts: 72
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
when i run this programme it outputs "false and F3=Nan" While answer says it should be f=4.2.
I am a bit confused which one is right and how, I just went through all the detail of Float.Nan and found that f=4.2 is right but why output is coming like F=Nan,
Please explain

 
Ranch Hand
Posts: 327
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
How are you running the code? Assertions on or off?

f2 is NaN (line 5, f2=f1).

With assertions off, the "assert" statement won't do anything.
f3 become 1.5
Then f3+f2 is i.1 + NaN which is always NaN.

If you run with assertions on, you'll get a different answer as the assert will cause an axception (NaN==NaN is false).

Is this from K&B? You should quote your sources.
 
Ranch Hand
Posts: 537
Eclipse IDE Python Java
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
If assertions are on then f = 4.2 is the answer. If its not then f = NaN. use java -ea AssertTest for f = 4.2
 
Ranch Hand
Posts: 808
1
Android Eclipse IDE Java
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
You must notice that:
float f1=Float.NaN;
float f2=f1;
f1==f2 => FALSE
 
Java Cowboy
Posts: 16084
88
Android Scala IntelliJ IDE Spring Java
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Section 15.21.1 of the Java Language Specification:

Floating-point equality testing is performed in accordance with the rules of the IEEE 754 standard:

  • If either operand is NaN, then the result of == is false but the result of != is true. Indeed, the test x!=x is true if and only if the value of x is NaN. (The methods Float.isNaN and Double.isNaN may also be used to test whether a value is NaN.)
  • Positive zero and negative zero are considered equal. Therefore, -0.0==0.0 is true, for example.
  • Otherwise, two distinct floating-point values are considered unequal by the equality operators. In particular, there is one value representing positive infinity and one value representing negative infinity; each compares equal only to itself, and each compares unequal to all other values.

  • Subject to these considerations for floating-point numbers, the following rules then hold for integer operands or for floating-point operands other than NaN:
  • The value produced by the == operator is true if the value of the left-hand operand is equal to the value of the right-hand operand; otherwise, the result is false.
  • The value produced by the != operator is true if the value of the left-hand operand is not equal to the value of the right-hand operand; otherwise, the result is false.
  •  
    "I know this defies the law of gravity... but I never studied law." -B. Bunny Defiant tiny ad:
    Building a Better World in your Backyard by Paul Wheaton and Shawn Klassen-Koop
    https://coderanch.com/wiki/718759/books/Building-World-Backyard-Paul-Wheaton
    reply
      Bookmark Topic Watch Topic
    • New Topic