String concatenation in mapper class of a MapReduce Program giving errors - mapreduce

Question

In my mapper class I want to do a small manipulation to a string read from a file(as a line) and then send it over to the reducer to get a string count. The manipulation being replace null strings with 0. (the current replace & join part is failing my hadoop job)
Here is my code:
import java.io.BufferedReader;
import java.io.IOException;
.....
public class PartNumberMapper extends MapReduceBase implements Mapper<LongWritable, Text, Text, IntWritable> {
private static Text partString = new Text("");
private final static IntWritable count = new IntWritable(1);
public void map(LongWritable key, Text value, OutputCollector<Text, IntWritable> output, Reporter reporter) throws IOException {
String line = value.toString();
// Read line by line to bufferreader and output the (line,count) pair
BufferedReader bufReader = new BufferedReader(new StringReader(line));
String l=null;
while( (l=bufReader.readLine()) != null )
{
/**** This part is the problem ****/
String a[]=l.split(",");
if(a[1]==""){ // if a[1] i.e. second string is "" then set it to "0"
a[1]="0";
l = StringUtils.join(",", a); // join the string array to form a string
}
/**** problematic part ends ****/
partString.set(l);
output.collect(partString, count);
}
}
}
After this is run, the mapper just fails and doesn't post any errors.
[The code is run with yarn]
I am not sure what I am doing wrong, the same code worked without the string join part.
Could any of you explain what is wrong with the string replace/concat? Is there a better way to do it?

Answer 1

Here's a modified version of your Mapper class with a few changes:
Remove the BufferedReader, it seems redundant and isn't being closed
String equality should be .equals() and not ==
Declare a String array using String[] and not String a[]
Resulting in the following code:
public class PartNumberMapper extends MapReduceBase implements Mapper<LongWritable, Text, Text, IntWritable> {
private Text partString = new Text();
private final static IntWritable count = new IntWritable(1);
public void map(LongWritable key, Text value, OutputCollector<Text, IntWritable> output, Reporter reporter) throws IOException {
String line = value.toString();
String[] a = l.split(",");
if (a[1].equals("")) {
a[1] = "0";
l = StringUtils.join(",", a);
}
partString.set(l);
output.collect(partString, count);
}
}