RoundRobinTableInputFormat.java

public class RoundRobinTableInputFormat extends TableInputFormat {
 @Override
 public List<InputSplit> getSplits(JobContext context) throws IOException {
        List<InputSplit> inputSplits = super.getSplits(context);  // Get splits from HBase TableInputFormat gives
        List<InputSplit> roundRobinInputSplits = new ArrayList<InputSplit>();
        Map<String, List<InputSplit>> regionServersInputSplits = new HashMap<String, List<InputSplit>>();
        // Prepare a hashmap with each region server as key and list of Input Splits as value
        if (inputSplits != null && inputSplits.size() != 0) {
            for (InputSplit inputSplit : inputSplits) {
                if (inputSplit instanceof TableSplit) {
                    String regionServer = ((TableSplit) inputSplit).getRegionLocation();
                    if (!Strings.isNullOrEmpty(regionServer)) {
                        List<InputSplit> splitList = regionServersInputSplits.get(regionServer);
                        if (splitList == null) {
                            splitList = new LinkedList<InputSplit>();
                            regionServersInputSplits.put(regionServer, splitList);
                        }
                        splitList.add(inputSplit);
                        continue;
                    }
                }
                // If TableSplit or region server not found, add it.
                roundRobinInputSplits.add(inputSplit);
            }
        } 
        while (true) { //For each regionServer keep adding one split, till all are added
            if (regionServersInputSplits.isEmpty()) {
                break;
            }
            Iterator<String> iterator = regionServersInputSplits.keySet().iterator();
            while (iterator.hasNext()){
                String regionServer = iterator.next();
                List<InputSplit> inputSplitListForRegion = regionServersInputSplits.get(regionServer);
                if(! inputSplitListForRegion.isEmpty()) {
                    roundRobinInputSplits.add(inputSplitListForRegion.remove(0));
                }
                if(inputSplitListForRegion.isEmpty()) {
                    iterator.remove();
                }
            }
        }
        return roundRobinInputSplits;
    }

while (true) { //For each regionServer keep adding one split, till all are added
if (regionServersInputSplits.isEmpty()) {
break;
}
...
}

could be replaced with

while (!regionServersInputSplits.isEmpty()) {
...
}

"inputSplits.size() != 0" VS "inputSplits.isEmpty()"

http://pmd.sourceforge.net/pmd-4.3.0/rules/design.html

Is it ok putting this class over here apache/hbase#2947 ? Thanks (and thanks for the nice accompanying blog).