This website has answered my question somewhat: http://blog.pfa-labs.com/2010/01/first-stab-at-hadoop-and-map-reduce.html
When I comment out the combiner class, it seems to work fine. Thanks. ----- Original Message ----- From: "Arindam Khaled" <akha...@utdallas.edu> To: common-user@hadoop.apache.org Sent: Monday, November 15, 2010 6:05:58 PM Subject: wrong value class error Hello, I am new to Hadoop and I think I'm doing something silly. I sent this e-mail from another account which isn't registered to hadoop user group. I am getting the following error in my reducer. 10/11/15 15:29:11 WARN mapred.LocalJobRunner: job_local_0001 java.io.IOException: wrong value class: class org.apache.hadoop.io.Text is not class org.apache.hadoop.io.IntWritable Here is my reduce class: public static class BFIDAReducer extends Reducer<Text,IntWritable,Text,Text> { private Text result = new Text(); public void reduce(Text key, Iterable<IntWritable> values, Context context ) throws IOException, InterruptedException { Text result = new Text(); GameFunctions gf = GameFunctions.getInstance(); String line = ""; for(IntWritable val: values) { line = line + val.toString() + ","; } if(line.length() > 1) line = (String) line.subSequence(0, line.length() - 1); if (gf.isSolved(key.toString(), size)) solved = true; result.set(line); context.write(key, result); } } And here is my partial code from job configuration: job.setOutputKeyClass(Text.class); job.setOutputValueClass(Text.class); job.setMapOutputKeyClass(Text.class); job.setMapOutputValueClass(IntWritable.class); Can anyone help me? I know I'll have more question in near future. Thanks in advance. Arindam