Question

I’m running a simple wordcount program, and I get the following error:

Type mismatch in key from map: expected org.apache.hadoop.io.Text, received org.apache.hadoop.io.LongWritable

What is the meaning of this, and how do I rectify it??

Answer 1

You can use either of the following lines in your main function:

 conf.setMapOutputKeyClass(Text.class);
 conf.setMapOutputValueClass(IntWritable.class);

assuming you’re using JobConf conf;

OR

    job.setMapOutputKeyClass(Text.class);
    job.setMapOutputValueClass(IntWritable.class);

assuming you’re using Job job = new Job();