Future接口和Callable接口的使用

 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;
 import  java.util.concurrent.FutureTask;

 public   class  ConcurrentCalculator {

    private  ExecutorService exec;
    private   int  cpuCoreNumber;
    private  List<Future<Long>> tasks =  new  ArrayList<Future<Long>>();

    // 内部类
    class  SumCalculator  implements  Callable<Long> {  //线程中用来计算的部分，相当于run（）方法
        private   int [] numbers;
        private   int  start;
        private   int  end;

        public  SumCalculator( final   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  ConcurrentCalculator() {
        cpuCoreNumber = Runtime.getRuntime().availableProcessors();
        exec = Executors.newFixedThreadPool(cpuCoreNumber);
    }

    public  Long sum( final   int [] numbers) {
        // 根据CPU核心个数拆分任务，创建FutureTask并提交到Executor
        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);
            FutureTask<Long> task = new  FutureTask<Long>(subCalc);  //线程
            tasks.add(task);
            if  (!exec.isShutdown()) {
                exec.submit(task);        //执行线程
            }
        }
        return  getResult();
    }

    /**
      * 迭代每个只任务，获得部分和，相加返回
      *
      * @return
      */
    public  Long getResult() {
        Long result = 0l;
        for  (Future<Long> task : tasks) {
            try  {
                // 如果计算未完成则阻塞
                Long subSum = task.get();   //得到每个线程的计算结果
                result += subSum;
            } catch  (InterruptedException e) {
                e.printStackTrace();
            } catch  (ExecutionException e) {
                e.printStackTrace();
            }
        }
        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 ,  10 ,  11  };
        ConcurrentCalculator calc = new  ConcurrentCalculator();
        Long sum = calc.sum(numbers);
        System.out.println(sum);
        calc.close();

    }
}