How to calculate Maximum salary of the employee with the name using the Map Reduce Technique

Question

Suppose i have file in HDFS with the below

EmpId,EmpName,Dept,Salary,

121,raj,Dept1,8000
122,Kiran,Dept2,6000
123,John,Dept3,9000

Using mapreduce i want to get only the max salary of employee and his name

i was able to get the max salary but not able to get the name.. I am able to get only the max salary by keeping the empty key in map class and Math.max() in reducer class, so that  I am able to get only max salary. when i keep the key as emp name then it is displaying all the salaries of unique employees.

Answer 1

Please try the below code and it might help you to get the required outputdown vpls try the following code. you will get the results.

public static class Mymap extends Mapper<LongWritable,Text,Text,Text>    
 {  
  public void map(LongWritable k,Text v, Context con)throws IOException, InterruptedException  
  {  
   String line = v.toString();  
   String[] w=line.split(",");  
   int sal=Integer.parseInt(w[3]);  
   string name=Integer.parseInt(w[1]);
   con.write(new Text(name), new Text(name+","+sal));  
   }  
 } 

 public static class MyRed extends Reducer<Text,Text,IntWritable,Text>  
 {  
  public void reduce(Text k, Iterable<Text> vlist, Context con)
  throws IOException , InterruptedException  
     {  
      int max=0;  
      for(Text v:vlist)  
   {
        String line = v.toString();  
        String[] w=line.split(",");  
        int sal=Integer.parseInt(w[1]); 
        max=Math.max(max, sal);
   }  
   con.write(new IntWritable(max), k);  
  }

 }