Type mismatch in key/value from map

When your working with Map-reduce job,
 If you are running into this error, "java.io.IOException: Type mismatch in key from map: expected org.apache.hadoop.io.Text, recieved org.apache.hadoop.io.LongWritable"

 solution: 
//your Map and/or Reduce implementation 
Map<Text,IntWritable,Text,IntWritable>(...)
 Reducer<Text,IntWritable,Text,IntWritable>(...) 

//the job configuration
 // Set the outputs for the Map 
 job.setMapOutputKeyClass(Text.class); 
job.setMapOutputValueClass(IntWritable.class);

 // Set the outputs for the Job 
job.setOutputKeyClass(Text.class); 
job.setOutputValueClass(IntWritable.class);


Some time generic map and reduce class will cause this kind problems