Community Articles
Find and share helpful community-sourced technical articles
Alert: Welcome to the Unified Cloudera Community. Former HCC members be sure to read and learn how to activate your account here.
Labels (1)
Cloudera Employee


I'm still seeing some people struggling to run their own mapreduce applications using a command line. For those who are not java developers, here is some quick guidance.

Let's create a new directory and put our new java extension within it.

import org.apache.hadoop.conf.*;
import org.apache.hadoop.mapreduce.*;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;

public class WordCount {

  public static class TokenizerMapper 
       extends Mapper<Object, Text, Text, IntWritable>{
    private final static IntWritable one = new IntWritable(1);
    private Text word = new Text();
    public void map(Object key, Text value, Context context
                    ) throws IOException, InterruptedException {
      StringTokenizer itr = new StringTokenizer(value.toString());
      while (itr.hasMoreTokens()) {
        context.write(word, one);
  public static class IntSumReducer 
       extends Reducer<Text,IntWritable,Text,IntWritable> {
    private IntWritable result = new IntWritable();

    public void reduce(Text key, Iterable<IntWritable> values, 
                       Context context
                       ) throws IOException, InterruptedException {
      int sum = 0;
      for (IntWritable val : values) {
        sum += val.get();
      context.write(key, result);

  public static void main(String[] args) throws Exception {
    Configuration conf = new Configuration();
    String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
    if (otherArgs.length != 2) {
      System.err.println("Usage: wordcount <in> <out>");
    Job job = new Job(conf, "word count");
    FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
    FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));
    System.exit(job.waitForCompletion(true) ? 0 : 1);

From the client-side, we need to be able to resolve external resources classes / libraries ( import lines ). Let's find out our hadoop classpath to resolve any dependency.:

-sh-4.1$ hadoop classpath
/usr/jdk64/jdk1.8.0_112/bin/javac -classpath $(/usr/hdp/current/hadoop-client/bin/hadoop classpath) -d job/ job/

Now, all the classes were turned into a .class, let's group them all into a single jar.

-sh-4.1$ /usr/jdk64/jdk1.8.0_112/bin/jar -cvf Test.jar -C job/ .

Execute the mapreduce program.

-sh-4.1$ hadoop jar Test.jar WordCount /tmp/sample_07.csv /tmp/output_mapred
17/11/05 23:41:50 INFO client.RMProxy: Connecting to ResourceManager at
17/11/05 23:41:51 INFO client.AHSProxy: Connecting to Application History server at
17/11/05 23:41:51 INFO hdfs.DFSClient: Created HDFS_DELEGATION_TOKEN token 12603 for bob1 on ha-hdfs:cluster2
17/11/05 23:41:51 INFO security.TokenCache: Got dt for hdfs://cluster2; Kind: HDFS_DELEGATION_TOKEN, Service: ha-hdfs:cluster2, Ident: (HDFS_DELEGATION_TOKEN token 12603 for bob1)
File Input Format Counters 
Bytes Read=46055
File Output Format Counters 
Bytes Written=36214
0 Kudos
Don't have an account?
Coming from Hortonworks? Activate your account here
Version history
Revision #:
1 of 1
Last update:
‎11-06-2017 03:19 PM
Updated by:
Top Kudoed Authors