java - MapReduce - reducer does not combine keys -

i have simple map reduce job building reverse index.

my mapper works correctly (i checked that) , outputs key pair of word , docid:tfidf value:

mapper (only output shown):

context.write(new intwritable(wordindex), new text(index + ":" + tfidf)); 

the job of reducer combine these values. implementation:

public static class indexerreducer extends reducer<text, intwritable, intwritable, text>     {         public void reduce(intwritable key, iterable<text> values, context context) throws ioexception, interruptedexception         {              stringbuilder sb = new stringbuilder();              (text value : values)             {                 sb.append(value.tostring() + " ");             }              context.write(key, new text(sb.tostring()));         }     } 

however, not combine , output looks same form mapper. there lines in output same key although reducer supposed combine them - keys in output file supposed unique when using reducer, right?

this sample of how reducer output looks (note simplified example):

1 15:2.1 1 13:4.3 2 9:9.3 2 43:7.9 etc 

i expected this:

1 15:2.1 13:4.3 2 9:9.3 43:7.9 

for sake of completeness, including run method:

@override     public int run(string[] arguments) throws exception {         argumentparser parser = new argumentparser("textpreprocessor");          parser.addargument("input", true, true, "specify input directory");         parser.addargument("output", true, true, "specify output directory");          parser.parseandcheck(arguments);          path inputpath = new path(parser.getstring("input"));         path outputdir = new path(parser.getstring("output"));          // create configuration.         configuration conf = getconf();          // add distributed file vocabulary         distributedcache                 .addcachefile(new uri("/user/myslima3/vocab.txt"), conf);          // create job.         job job = new job(conf, "wordcount");         job.setjarbyclass(indexermapper.class);          // setup mapreduce.         job.setmapperclass(indexermapper.class);         job.setreducerclass(indexerreducer.class);          // sort output words in reversed order.         job.setsortcomparatorclass(wordcountcomparator.class);           job.setnumreducetasks(1);          // specify (key, value).         job.setmapoutputkeyclass(intwritable.class);         job.setmapoutputvalueclass(text.class);         job.setoutputkeyclass(intwritable.class);         job.setoutputvalueclass(text.class);          // input.         fileinputformat.addinputpath(job, inputpath);         job.setinputformatclass(textinputformat.class);          // output.         fileoutputformat.setoutputpath(job, outputdir);         job.setoutputformatclass(textoutputformat.class);          filesystem hdfs = filesystem.get(conf);          // delete output directory (if exists).         if (hdfs.exists(outputdir))             hdfs.delete(outputdir, true);          // execute job.         return job.waitforcompletion(true) ? 0 : 1;     } 

i glad hint going on. new map reduce. debugging tips!

always use @override annotation.

you defined

public static class indexerreducer extends reducer<text, intwritable, intwritable, text> 

then reduce method must that

@override public void reduce(text key, iterable<intwritable> values, context context) throws ioexception, interruptedexception