Trouble with double byte swapping routine

Question

I'm working on a program that reads little endian doubles from a DataInputStream and then swaps them. Usually, everything works fine. However, certain values don't swap correctly.
I'm at a total loss as to why this is happening, so I hoped one of you guys could show me. I've included a demonstration program with the method I'm using to swap doubles.
public class SwapTest
     public static void main(String[] args)
          new SwapTest();
     public SwapTest()
          // The swap routine works well with this value
          double d = 0.8660252094218776d;
          System.out.println("d before being swapped: " + d);
          // Swap to small order, then back to big order
          d = swapBytes(d);
          d = swapBytes(d);
          System.out.println("d after being swapped: " + d);
          System.out.println();
          // Everything gets totally hosed with this value
          d = 0.8660252079425844d;
          System.out.println("d before being swapped: " + d);
          // Swap to small order, then back to big order
          d = swapBytes(d);
          d = swapBytes(d);
          System.out.println("d after being swapped: " + d);
     private static double swapBytes(double sm)
          long smallendian = Double.doubleToLongBits(sm);
          long result;
          long l1 = (smallendian & 0x00000000000000FFL) << 56;
          long l2 = (smallendian & 0x000000000000FF00L) << 40;
          long l3 = (smallendian & 0x0000000000FF0000L) << 24;
          long l4 = (smallendian & 0x00000000FF000000L) << 8;
          long l5 = (smallendian & 0x000000FF00000000L) >>> 8;
          long l6 = (smallendian & 0x0000FF0000000000L) >>> 24;
          long l7 = (smallendian & 0x00FF000000000000L) >>> 40;
          long l8 = (smallendian & 0xFF00000000000000L) >>> 56;
          result = l1 | l2 | l3 | l4 | l5 | l6 | l7 | l8;
          return Double.longBitsToDouble(result);
}

Answer 1

The doubleToLongBits() method converts invalid values to NAN before converting