Floating point bug?

Question

Hello,
Please, see this code:
  public static void main(String[] args)
    double[] arr=new double[]{3279.87d,-986.09d,-2293.78d};
    double d=0;
    double h=0;
    for(int i=0;i<arr.length;i++)
      double x=arr;
System.out.println(x);
if(x>0)
d+=x;
else
h-=x;
System.out.println("d = "+d);
System.out.println("h = "+h);
System.out.println("d-h= "+(d-h));
System.out.println("d==h= "+(d==h));
"d" and "h" must be equal.
However, it prints:
3279.87
-986.09
-2293.78
d = 3279.87
h = 3279.8700000000003
d-h= -4.547473508864641E-13
d==h= false
Is this a bug?
Using strictfp produces the same output.
JDK: 1.4.2_03 (linux) and 1.5.0 (linux)

Answer 1

Is this a bug? Using strictfp produces the same output.No, you just don't understand how floating point numbers work:
What Every Computer Scientist Should Know About Floating Point Numbers
Your own data is telling you that the difference between d and h is 1e-13, which is NOT zero. Since that's the case, how could d == h be true? Why don't you believe the evidence you have in front of you?
Anyone who works with floating point numbers would know that you don't check equality like that. You compare the absolute value of the difference to a small error value.