The sum is correct. There is no issue with floating point addition. I'm working with integers converted into floating point values. Therefore the addition order issue of floating point is not applicable for this particular scenario. Any kind of division is showing abnormal behaviour.
Eg: 1.0/sum is yeilding only sum. If I do sum/2.0 I'm not getting half of the sum
Issue is resolved. If anyone have similar problem, please check your Hadoop job configuration. I was using WordCount program template in my program. In that program there was Combiner class setup was specified. Due to that statement I got erroneous output. I commented that line and got correct output.