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According to the Java Language Specification \[[JLS 05|AA. Java References#JLS 05]\], Section 4.2.3, ""Floating-Point Types, Formats, and Values"": |
NaNis unordered, so the numerical comparison operators<,<=,>, and>=returnfalseif either or both operands areNaN. The equality operator==returnsfalseif either operand isNaN, and the inequality operator!=returnstrueif either operand isNaN.
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public class NaNComparison {
public static void main(String[] args) {
double x = 0.0;
double result = Math.cos(1/x); // returns NaN if input is infinity
if(result == Double.NaN) { // compare with infinity
System.out.println(""Both are equal"");
}
}
}
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Compliant Solution
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public class NaNComparison {
public static void main(String[] args) {
double x = 0.0;
double result = Math.cos(1/x); // returns NaN if input is infinity
if(Double.isNaN(result)) {
System.out.println(""Both are equal"");
}
}
}
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Risk Assessment
Comparisons with NaN values may lead to unexpected results.
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FLP01-J. Take care in rearranging floating point expressions 07. Floating Point (FLP) FLP03-J. Use the strictfp modifier for floating point calculation consistency