MapReduce problm

Dear team

I am trying to run the below program regarding the electrical consumption of an organization to produce results such as finding the year of maximum usage, year of minimum usage. But getting following Error:java.lang.NumberFormatException: null

Program:-
package hadoop;

import java.io.IOException;
import java.util.StringTokenizer;

import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import...

MapReduce problm