Hadoop Java Error : Exception in thread "main" java.lang.NoClassDefFoundError: WordCount (wrong name: org/myorg/WordCount)

try this,

import java.io.IOException;import java.util.Iterator;import java.util.StringTokenizer;import org.apache.hadoop.fs.Path;import org.apache.hadoop.io.IntWritable;import org.apache.hadoop.io.LongWritable;import org.apache.hadoop.io.Text;import org.apache.hadoop.mapred.FileInputFormat;import org.apache.hadoop.mapred.FileOutputFormat;import org.apache.hadoop.mapred.JobClient;import org.apache.hadoop.mapred.JobConf;import org.apache.hadoop.mapred.MapReduceBase;import org.apache.hadoop.mapred.Mapper;import org.apache.hadoop.mapred.OutputCollector;import org.apache.hadoop.mapred.Reducer;import org.apache.hadoop.mapred.Reporter;import org.apache.hadoop.mapred.TextInputFormat;import org.apache.hadoop.mapred.TextOutputFormat;public class WordCount {    public static class Map extends MapReduceBase implements            Mapper<LongWritable, Text, Text, IntWritable> {        @Override        public void map(LongWritable key, Text value, OutputCollector<Text, IntWritable> output, Reporter reporter)                throws IOException {            String line = value.toString();            StringTokenizer tokenizer = new StringTokenizer(line);            while (tokenizer.hasMoreTokens()) {                value.set(tokenizer.nextToken());                output.collect(value, new IntWritable(1));            }        }    }    public static class Reduce extends MapReduceBase implements            Reducer<Text, IntWritable, Text, IntWritable> {        @Override        public void reduce(Text key, Iterator<IntWritable> values,                OutputCollector<Text, IntWritable> output, Reporter reporter)                throws IOException {            int sum = 0;            while (values.hasNext()) {                sum += values.next().get();            }            output.collect(key, new IntWritable(sum));        }    }    public static void main(String[] args) throws Exception {        JobConf conf = new JobConf(WordCount.class);        conf.setJobName("wordcount");        conf.setOutputKeyClass(Text.class);        conf.setOutputValueClass(IntWritable.class);        conf.setMapperClass(Map.class);        conf.setReducerClass(Reduce.class);        conf.setInputFormat(TextInputFormat.class);        conf.setOutputFormat(TextOutputFormat.class);        FileInputFormat.setInputPaths(conf, new Path(args[0]));        FileOutputFormat.setOutputPath(conf, new Path(args[1]));        JobClient.runJob(conf);    }}

then run command

bin/hadoop jar WordCount.jar WordCount /hdfs_Input_filename /output_filename

if your code is in particular package then you have to mention package name with class name

bin/hadoop jar WordCount.jar PakageName.WordCount /hdfs_Input_filename /output_filename

This may sound crazy. I added package org.myorg; to my code and compiled it again. I placed the class files in org/myorg folder and created the jar file using them. Then I ran using the jar wc.jar org.myorg.WordCount command and it got executed successfully. It would be nice if someone could explain me how it actually ran :D . Any way, thanks a lot for helping me guys.

try explicitly including the nested classes(i.e. TokenizerMapper and IntSumReducer) in you jar file. Here is how I did it:

jar cvf WordCount.jar WordCount.class WordCount\$TokenizerMapper.class WordCount\$IntSumReducer.class