ColorMapperReducer.java

import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import org.apache.hadoop.fs.Path;
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;
import org.apache.hadoop.util.ReflectionUtils;

public class TestMapReduce {

	public static class ColorMapper extends Mapper<Object, Text, Text, ColorWritable> {

		private Text MyKey = new Text("A");

		public void map(Object key, Text value, Context context) throws IOException, InterruptedException
		{

			String word = value.toString();
			Context.write(MyKey, new ColorWritable(new Text(word)));

		}
	}

	public static class ColorReducer extends Reducer<Text, ColorWritable, Text, Text> 
	{

	    	   public void reduce(Text key, Iterator<ColorWritable> values,Context context) throws IOException 
		   {

			try {

				ArrayList<ColorWritable> list = new ArrayList<ColorWritable>();
				Configuration conf = context.getConfiguration();

				while (values.hasNext()) {

					ColorWritable n = ReflectionUtils.newInstance(
							ColorWritable.class, conf);
					ReflectionUtils.copy(conf, values.next(), n);
					list.add(n);
				}

				for (int i = 0; i < list.size(); i++) {
					ColorWritable c = list.get(i);
					output.collect(key, new Text(c.getColor()));
				}
			} catch (Exception e) {
				System.out.println(e.toString());
			}
		}

	}

	public static void main(String[] args) {

		try {
			JobConf conf = new JobConf(TestMapReduce.class);
			conf.setJobName("Iterator Comparable");

			conf.setOutputKeyClass(Text.class);
			conf.setOutputValueClass(ColorWritable.class);

			conf.setMapperClass(CountMapper.class);
			conf.setReducerClass(CountReducer.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);

		} catch (Exception e) {
			System.out.println(e.toString());
		}
	}

}