Count Frequency of Character in Mapreduce Programme

• Kiran Dalvi
• 20 Dec, 2021
• 0 Comments
• 1 Min Read

Count Frequency of Character in Mapreduce Programme

Mapper Programe

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package wordcount;   import java.io.IOException;   import org.apache.hadoop.io.LongWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Mapper;   public class AlphaMapper extends Mapper<Object, Text, Text, LongWritable> { private final static LongWritable one = new LongWritable(1); private Text character = new Text();   @Override public void map(Object key, Text value, Context context) throws IOException, InterruptedException { String v = value.toString(); for (int i = 0; i < v.length(); i++) { character.set(v.substring(i, i + 1)); context.write(character, one); } } }

Reducer Programe

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package wordcount;   import java.io.IOException;   import org.apache.hadoop.io.LongWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Reducer;      public class AlphaReducer extends Reducer<Text, LongWritable, Text, LongWritable> {     private LongWritable result = new LongWritable();        public void reduce(Text key, Iterable<LongWritable> values, Context context)             throws IOException, InterruptedException {         long sum = 0;         for (LongWritable val : values) {             sum += val.get();         }         result.set(sum);         context.write(key, result);     } }

Driver Programe

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import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.conf.Configured; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.LongWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Job; import org.apache.hadoop.mapreduce.lib.input.FileInputFormat; import org.apache.hadoop.mapreduce.lib.input.TextInputFormat; import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat; import org.apache.hadoop.util.Tool; import org.apache.hadoop.util.ToolRunner;    // The driver program for mapreduce job. public class AlphaCounter extends Configured implements Tool {        public static void main(String[] args) throws Exception {         int res = ToolRunner.run(new Configuration(), new AlphaCounter(), args);         System.exit(res);     }        @Override     public int run(String[] args) throws Exception {            Configuration conf = this.getConf();            // Create job         Job job = Job.getInstance(conf, "Alpha Counter Job");         job.setJarByClass(AlphaCounter.class);            job.setMapperClass(AlphaMapper.class);         job.setReducerClass(AlphaReducer.class);            job.setOutputKeyClass(Text.class);         job.setOutputValueClass(LongWritable.class);            FileInputFormat.addInputPath(job, new Path(args[0]));         job.setInputFormatClass(TextInputFormat.class);            FileOutputFormat.setOutputPath(job, new Path(args[1]));         job.setOutputFormatClass(TextOutputFormat.class);            return job.waitForCompletion(true) ? 0 : 1;     } }

Run Mapreduce Programe

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hadoop jar count.jar wordcount.AlphaCounter /user/hive/input/wordcount.txt /user/hive/output/wordcount1               14 I       1 a       10 c       2 d       4 e       9 g       6 h       2 i       5 l       3 m       7 n       4 o       8 p       4 r       9 s       3 u       3 w       2 y       2