FULL PRODUCT VERSION :
java version "1.6.0_20"
Java(TM) SE Runtime Environment (build 1.6.0_20-b02)
Java HotSpot(TM) Client VM (build 16.3-b01, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Windows XP Pro (ver 5.1.2600)

A DESCRIPTION OF THE PROBLEM :
A null result is returned in the last line of code instead of a .tiff ImageReader. This same code returns an ImageReader in JDK 1.5:

Iterator<ImageWriter> writers = ImageIO.getImageWritersByFormatName("tiff");
ImageWriter tiffImageWriter = writers.next();
tiffImageWriter.setOutput(imageOutputStream);
ImageReader tiffImageReader = ImageIO.getImageReader(tiffImageWriter);

Replacing the getImageReader method with the getImageReadersByFormatName method permits the retrieval of a valid .tiff ImageReader. Thus, replacing the last line above with the two following lines will return a reader instead of a null:

Iterator<ImageReader> readers = ImageIO.getImageReadersByFormatName("tiff");
ImageReader tiffImageReader = readers.next();


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
See description.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
tiff ImageReader

ERROR MESSAGES/STACK TRACES THAT OCCUR :
No error until you try to use tiffImageReader, then a NullPointerException occurs.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
Iterator<ImageWriter> writers = ImageIO.getImageWritersByFormatName("tiff");
ImageWriter tiffImageWriter = writers.next();
tiffImageWriter.setOutput(imageOutputStream);
ImageReader tiffImageReader = ImageIO.getImageReader(tiffImageWriter);
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Use ImageIO.getImageReadersByFormatName("tiff")