public void run() {
GATKSAMIterator downsamplingIter = new PerSampleDownsamplingReadsIterator(mergedReadStream.getGATKSAMIterator(), downsamplerFactory);
if ( verifySortedness ) {
downsamplingIter = new VerifyingSamIterator(downsamplingIter);
}
while ( downsamplingIter.hasNext() ) {
SAMRecord read = downsamplingIter.next();
String sampleName = read.getReadGroup() != null ? read.getReadGroup().getSample() : null;