What's wrong with using == to compare floats in Java?

java equality floating-accuracy
user128807 picture user128807 · Jul 6, 2009 · Viewed 160.4k times · Source

According to this java.sun page == is the equality comparison operator for floating point numbers in Java.

However, when I type this code:

if(sectionID == currentSectionID)

into my editor and run static analysis, I get: "JAVA0078 Floating point values compared with =="

What is wrong with using == to compare floating point values? What is the correct way to do it? 

Answer

Victor picture Victor · Jul 6, 2009

the correct way to test floats for 'equality' is:

if(Math.abs(sectionID - currentSectionID) < epsilon)

where epsilon is a very small number like 0.00000001, depending on the desired precision.

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