Multi Thread Processing in Java

Question

Im just having a few issues getting my head around this problem. Any help would be greatly appreciated.

The program must read a text file, where it will compute the sum of divisors of each input number. For example, number 20 has the sum 1+2+4+5+10=22. Then these sums are summed up line-by-line. For each of these sums above the divisor is then found, and then finally they are totaled up.

E.g Initial File 1 2 4 6 15 20

25 50 100 125 250 500

16 8 3

Then computes the sum of divisors.

1 1 3 6 9 22

6 43 117 31 218 592

15 7 1

Summed up line by line

42

1007

23

Then above sums are computed.

54

73

1

Then finally totaled up and returned.

128

I need to complete the process with each new line being completed by a threadpool.

My logic is as follows.

              5.2. For each input line (Add each line to an ArrayBlockingQueue, 
Then add each item in the Queue to an ExecutorService Which will run the follow)   

               5.2.1. Parse the current input line into integers 

               5.2.2. For each integer in the current input line 

                   5.2.2.1. Compute the sum-of-divisors of this integer 

                   5.2.2.2. Add this to the cumulated sum-of-divisors 

               5.2.3. Compute the sum-of-divisors of this cumulated sum

               5.2.4. Add this to the grand total

I get stuck after 5.2, Do I either create a new class that implements the runnable interface and then adds the cumulated sum to an atomicArray, or is best to create a class that implements the callable interface and then get it to return the cumulated sum? Or is there a completely different way.

Here is what i have so far which returns the desired result but in a sequential matter.

http://pastebin.com/AyB58fpr

Answer 1

I prefer the Callable interface since that doesn't create a dependency of the code which processes the input to how the output is gathered.

The usual approach is to collect the tasks in a list of Futures. See this answer for an example.

Answer 2

Use

java.util.concurrent.Future

and a

java.util.concurrent.Executors.newFixedThreadPool(int nThreads)

This will be really easy to do.

Follow the Oracle tutorial if you are not familiar with Executors.