The first program of Hadoop Big Data--wordcount

Map class:

1  PackageLYC.YUSHAO.HADOOP.MR.WC;2 3 Importjava.io.IOException;4 5 Importorg.apache.hadoop.io.LongWritable;6 ImportOrg.apache.hadoop.io.Text;7 ImportOrg.apache.hadoop.mapreduce.Mapper;8 9  Public classWcmapperextendsmapper<longwritable, text, text, longwritable> {Ten  One @Override A     protected voidmap (longwritable key, Text value, context context) -             throwsIOException, interruptedexception { -         //first, receive the data the         //Accept Data -String line =value.tostring (); -         //to split -         //Split +string[] Words = Line.split (""); -         //to cycle +         //Loop A          for(String w:words) { at             //Send -             //Send -Context.write (NewText (W),NewLongwritable (1)); -         } -  -     } in  -}

Reduce class:

1  PackageLYC.YUSHAO.HADOOP.MR.WC;2 3 Importjava.io.IOException;4 5 Importorg.apache.hadoop.io.LongWritable;6 ImportOrg.apache.hadoop.io.Text;7 ImportOrg.apache.hadoop.mapreduce.Reducer;8 9  Public classWcreducerextendsReducer<text, Longwritable, Text, longwritable> {Ten  One @Override A     protected voidReduce (Text key, iterable<longwritable>values, -Context context)throwsIOException, interruptedexception { -         //Define a counter the         //Define a counter -         LongCounter = 0; -  -         //receiving data Loops +         //Accept data and loop -          for(longwritable i:values) { +             //sum ACounter + =i.get (); at  -         } -         //Send -Context.write (Key,Newlongwritable (counter)); -  -     } in  -}

WordCount class:

1  PackageLYC.YUSHAO.HADOOP.MR.WC;2 3 Importorg.apache.hadoop.conf.Configuration;4 ImportOrg.apache.hadoop.fs.Path;5 Importorg.apache.hadoop.io.LongWritable;6 ImportOrg.apache.hadoop.io.Text;7 ImportOrg.apache.hadoop.mapreduce.Job;8 ImportOrg.apache.hadoop.mapreduce.lib.input.FileInputFormat;9 ImportOrg.apache.hadoop.mapreduce.lib.output.FileOutputFormat;Ten  One  Public classWordCount { A  -      Public Static voidMain (string[] args)throwsException { -Configuration conf =NewConfiguration (); the         //abstract MapReduce into a single job -Job Job =job.getinstance (conf); -  -         //Notice!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! +Job.setjarbyclass (WordCount.class); -  +         //assemble a custom class A  at         //Set Mapper ' s properties -Job.setmapperclass (Wcmapper.class); -  -Job.setmapoutputkeyclass (Text.class); -  -Job.setmapoutputvalueclass (longwritable.class); in  -         //reading HDFs Data toFileinputformat.setinputpaths (Job,NewPath ("/words.txt")); +  -         //Set Reducer ' s properties theJob.setreducerclass (Wcreducer.class); *         //output to HDFs inside $Job.setoutputkeyclass (Text.class);Panax NotoginsengJob.setoutputvalueclass (longwritable.class); -Fileoutputformat.setoutputpath (Job,NewPath ("/wcout111")); the  +         //Some methods of invoking the job to commit A         //submit,but This isn't good the         //job.submit (); +Job.waitforcompletion (true); -     } $  $}

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The first program of Hadoop Big Data--wordcount