JDK5.0 ThreadPool 多线程计算

package karl.test.threadpool;

import java.util.concurrent.Callable;
import java.util.concurrent.CompletionService;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorCompletionService;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class ConcurrentCalculator2 {
    private ExecutorService exec;

    private CompletionService<Long> completionService;

    private int cpuCoreNumber;

    class SumCalculator implements Callable<Long> {
        private int[] numbers;

        private int start;

        private int end;

        public SumCalculator(int[] numbers, int start, int end) {
            this.numbers = numbers;
            this.start = start;
            this.end = end;
        }

        public Long call() throws Exception {
            Long sum = 0L;
            for (int i = start; i < end; i++) {
                sum += numbers[i];
            }
            return sum;
        }

    }

    public ConcurrentCalculator2() {
        cpuCoreNumber = Runtime.getRuntime().availableProcessors();
        exec = Executors.newFixedThreadPool(cpuCoreNumber);
        completionService = new ExecutorCompletionService<Long>(exec);
    }

    public Long sum(final int[] numbers) {
        for (int i = 0; i < cpuCoreNumber; i++) {
            int increment = numbers.length / cpuCoreNumber + 1;
            int start = increment * i;
            int end = increment * i + increment;
            if (end > numbers.length) {
                end = numbers.length;
            }
            SumCalculator subCalc = new SumCalculator(numbers, start, end);
            if (!exec.isShutdown()) {
                completionService.submit(subCalc);
            }
        }
        return getResult();
    }

    public Long getResult() {
        Long result = 0L;
        for (int i = 0; i < cpuCoreNumber; i++) {
            try {
                Long subSum = completionService.take().get();//take()已经完成的任务，如果暂时还没有完成的任务，take()方法也会阻塞。
                result += subSum;
            } catch (InterruptedException e) {
            } catch (ExecutionException e) {
            }
        }
        return result;
    }

    public void close() {
        exec.shutdown();
    }

    public static void main(String[] args) {
        int[] numbers = new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 };
        ConcurrentCalculator2 calc = new ConcurrentCalculator2();
        Long sum = calc.sum(numbers);
        System.out.println(sum);
        calc.close();
    }
}