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

Question

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

However, when I type this code:

Answer 1

The following automatically uses the best precision:

/**
 * Compare to floats for (almost) equality. Will check whether they are
 * at most 5 ULP apart.
 */
public static boolean isFloatingEqual(float v1, float v2) {
    if (v1 == v2)
        return true;
    float absoluteDifference = Math.abs(v1 - v2);
    float maxUlp = Math.max(Math.ulp(v1), Math.ulp(v2));
    return absoluteDifference < 5 * maxUlp;
}

Of course, you might choose more or less than 5 ULPs (‘unit in the last place’).

If you’re into the Apache Commons library, the Precision class has compareTo() and equals() with both epsilon and ULP.