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According to the JLS:

"NaN is unordered, so the numerical comparison operators <, <=, >, and >= return false if either or both operands are NaN. The equality operator == returns false if either operand is NaN, and the inequality operator != returns true if either operand is NaN."

...

public class NaNComparison {
  public static void main(String[] args) {
    double result = Double.NaN;
  if(Double.isNaN(result)) 
    System.out.println("Both are equal");
  }
}

Risk Assessment

Comparisons with NaN values may lead to unexpected results.

Automated Detection

TODO

Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

References

\[[JLS 05|AA. Java References#JLS 05]\] Section 4.2.3 Floating-Point Types, Formats, and

 Values
\[[FindBugs 08|AA. Java References#FindBugs 08]\] FE: Doomed test for equality to NaN