A Hadoop Word Count example using my own map and reduce classes. Tested with Java 1.6 and Hadoop 1.0.4.

MyWordCount.java

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

public class MyWordCount {

    public static class MyWordCountMapper 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 {
            for (String str : value.toString().toLowerCase().split("[\\W\\s]+")) {
                word.set(str);
                context.write(word, one);
            }
        }
    }

    public static class MyWordCountReducer extends Reducer<Text, IntWritable, Text, IntWritable> {
        public void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
            int total = 0;
            for (IntWritable val : values) total += val.get();
            context.write(key, new IntWritable(total));
        }
    }

    public static void main(String[] args) throws Exception {
        Job job = new Job(new Configuration(), "My Word Count");

        job.setJarByClass(MyWordCount.class);
        job.setMapperClass(MyWordCountMapper.class);
        job.setCombinerClass(MyWordCountReducer.class);
        job.setReducerClass(MyWordCountReducer.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(IntWritable.class);

        FileInputFormat.addInputPath(job, new Path(args[0]));
        FileOutputFormat.setOutputPath(job, new Path(args[1]));

        System.exit(job.waitForCompletion(true) ? 0 : 1);
    }
}