Software Engineering for Smart Data Analytics & Smart Data Analytics for Software Engineering

This code checks to see if a floating point value is equal to the special `Not A Number`

value (e.g., if `(x == Double.NaN)`

). However, because of the special semantics of NaN, no value is equal to NaN, including NaN. Thus, `x == Double.NaN`

always evaluates to false. To check to see if a value contained in x is the special `Not A Number`

value, use `Double.isNaN(x)`

(or `Float.isNaN(x)`

if x is floating point precision).
– 2013-10-15

When working with floating point variables (such as `Float`

and `Double`

) one often wants to test if an invalid operation has been invoked. To this end one should use the `Float.isNaN(f)`

function and do **NOT** test equality to the public constant `NaN`

defined in the `Float`

or `Double`

class. As a matter of fact, no variable will ever be equal to the NaN constant, due to its special semantics.

NaN is just a variable defined in many programming languages to give a “meaningful” result to operations that otherwise have no mathematically defined result. The value NaN (Not a number) results from the following operations:

- Complex values
- √x where x is negative
- log(x) where x is negative
- tan(x) where x mod 180 is 90
- asin(x) or acos(x) where x is outside [-1..1]

- 0/0
- ∞/∞
- ∞/−∞
- −∞/∞
- −∞/−∞
- 0×∞
- 0×−∞
- 1∞
- ∞ + (−∞)
- (−∞) + ∞

<code Java> Float f; if (f == Float.NaN){

System.out.println("IS NAN");

}

Double d; if (d == Double.NaN){

System.out.println("IS NAN");

} </Code>

<code Java>

Float f; if (Float.isNaN(f)){

System.out.println("IS NAN");

}

Double d; if (Double.isNaN()){

System.out.println("IS NAN");

} </Code>

Benchmark project | Time | # Hits | Precision | Recall | |||||
---|---|---|---|---|---|---|---|---|---|

FB | JT | FB | JT | Delta | FB | JT | Delta | ||

Apache Tomcat | < 1s | 0 | 0 | 100% | 100% | 0 | 100% | 100% | 0 |

Argo UML | < 1s | 0 | 0 | 100% | 100% | 0 | 100% | 100% | 0 |

AWT | < 1s | 0 | 0 | 100% | 100% | 0 | 100% | 100% | 0 |

Jakarta | < 1s | 0 | 0 | 100% | 100% | 0 | 100% | 100% | 0 |

Java IO | < 1s | 0 | 0 | 100% | 100% | 0 | 100% | 100% | 0 |

JHotDraw | < 1s | 0 | 0 | 100% | 100% | 0 | 100% | 100% | 0 |

jrefactory | < 1s | 0 | 0 | 100% | 100% | 0 | 100% | 100% | 0 |

JServlet | < 1s | 0 | 0 | 100% | 100% | 0 | 100% | 100% | 0 |

JUnit | < 1s | 0 | 0 | 100% | 100% | 0 | 100% | 100% | 0 |

Lexi | < 1s | 0 | 0 | 100% | 100% | 0 | 100% | 100% | 0 |

Mapper XML | < 1s | 0 | 0 | 100% | 100% | 0 | 100% | 100% | 0 |

nutch | < 1s | 0 | 0 | 100% | 100% | 0 | 100% | 100% | 0 |

PMD | < 1s | 0 | 0 | 100% | 100% | 0 | 100% | 100% | 0 |

quickuml | < 1s | 0 | 0 | 100% | 100% | 0 | 100% | 100% | 0 |

FB = FindBugs, JT = JTransformer, Delta = JTransformer - FindBug

All measurements were taken on a machine with the following properties:

- JT Version: 4.0.0
- Eclipse Kepler
- Windows 8.1
- i5 2,30Ghz
- 8 GB Main Memory
- SSD Hardrive

teaching/labs/mdse/2013/bug_descriptions/jt-bug-cor46.txt · Last modified: 2018/05/09 01:59 (external edit)

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