淘宝面试题：如何充分利用多核CPU，计算很大的List中所有整数的和

import java.math.BigInteger;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;


public class Sum {
	public static void main(String[] args) throws InterruptedException, ExecutionException {
		List<Integer> testList = new ArrayList<Integer>();
		int min = Integer.parseInt(args[0]);
		int max = Integer.parseInt(args[1]);
		int threadNum = Integer.parseInt(args[2]);
		for (int i=min;i<=max;i++) testList.add(i);
		System.out.println(new Sum().countIntegerList(threadNum, testList));
	}
	
	BigInteger countIntegerList(int threadNum,List<Integer> list) throws InterruptedException, ExecutionException
	{
		BigInteger result= new BigInteger("0");
		ExecutorService es =  Executors.newFixedThreadPool(threadNum);
		List<ListTask> sumList= new ArrayList<ListTask>();
		int totalCount = list.size();
		int threadCount=totalCount/(threadNum-1);
		for (int i=0;i<threadNum;i++)
		{
			if (i == threadNum-1) sumList.add(new ListTask(list,i*threadCount,totalCount-1));
			else sumList.add(new ListTask(list,i*threadCount,(i+1)*threadCount-1));
		}
		List<Future<BigInteger>> resList =  es.invokeAll(sumList);
		for (int i=0;i<resList.size();i++) 
		{
			result  =result.add(resList.get(i).get());
		}
		es.shutdown();
		return result;
	}
	
	class ListTask  implements Callable<BigInteger>
	{
		private volatile List<Integer> list;
		private int start;
		private int end;
		
		public ListTask(List<Integer> list,int start,int end) {
			this.list = list;
			this.start= start;
			this.end = end;
		}

		public BigInteger call() throws Exception {
			BigInteger result = new BigInteger("0");
			for(int i=start;i<=end;i++) result = result.add(new BigInteger(String.valueOf(list.get(i))));
			return result;
		}
		
	}
}