Count Frequency of Character in Mapreduce Programme
Mapper Programe
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
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
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
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
