多線程處理list 求和

import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.*;

/**
 * Created by 45033535 on 2021/5/19.
 */
public class MultithreadingListSum {

    private int sum = 0;
    /**
     * @Description:   多個線程求和
     * @Version:   1.0
     */
    public static  class  ShareData implements Callable<Integer> {
        private  volatile  int startIndex ;
        private volatile  int endIndex ;
        private  volatile  int sum  ;

        private volatile List<JavaBean> list;
        private volatile int remaider;  //(先計算出餘數)
        private volatile int num;  //然後是商
        private volatile int offset = 0;//偏移量

        public  ShareData(int startIndex,int endIndex,List<JavaBean> list){
            this.startIndex = startIndex;
            this.endIndex = endIndex;
            this.list = list;
        }
        public ShareData(){}

        /**
         * 累加和
         * @return
         * @throws Exception
         */
        @Override
        public Integer call() throws Exception {
            System.out.println("子線程名稱:"+Thread.currentThread().getName()+"List 正在進行計算startIndex=="+ startIndex+"到 endIndex="+endIndex);

            List<JavaBean> arr = list.subList(startIndex,endIndex);
            System.out.println("arr"+arr);
            for(JavaBean bean : arr){
                sum +=bean.getAge();
                System.out.println("當前線程名稱:"+Thread.currentThread().getName()+"的和爲:"+sum);
            }

            //爲了空格方便好看
            System.out.println();
            System.out.println();
            System.out.println();
            return sum;
        }

        /**
         * 多線程求和startIndex~endIndex
         * @param list
         * @param threadNumber
         * @return
         */
        public Integer getDataSum(List<JavaBean> list ,int threadNumber){

            List<Future<Integer>> taskList = new CopyOnWriteArrayList<>();
            ExecutorService executorService = Executors.newFixedThreadPool(threadNumber);//固定指定線程數量


            try {

                 remaider = list.size() % threadNumber;  //(先計算出餘數)
                 num = list.size() / threadNumber;  //然後是商
                 offset = 0;//偏移量

                for (int i = 0; i < threadNumber; i++) {
                    if (remaider > 0) {
                        startIndex  = i * num + offset;
                        endIndex = (i + 1) * num + offset + 1;
                        remaider--;
                        offset++;

                        System.out.println("第"+i+",組索引:"+startIndex+","+endIndex);
                        Future future = executorService.submit(new MultithreadingListSum.ShareData(startIndex,endIndex,list));
                        //把每個子線程計算結果放到集合中
                        taskList.add(future);
                    } else {
                         startIndex = i * num + offset;
                         endIndex = (i + 1) * num + offset;

                        System.out.println("第"+i+",組索引:"+startIndex+","+endIndex);
                        Future future = executorService.submit(new MultithreadingListSum.ShareData(startIndex,endIndex,list));
                        //把每個子線程計算結果放到集合中
                        taskList.add(future);
                    }

                }
            }catch (Exception e){
                e.printStackTrace();
            }finally {
                executorService.shutdown();
            }
            //把各個集合中的值遍歷求和
            sum = getFutureSum(taskList);
            return  sum;
        }

        /**
         * 遍歷結果集，取數
         * @param taskList
         * @return
         */
        public Integer getFutureSum(List<Future<Integer>> taskList) {
            int sumNumber = 0;
            if (taskList.size() == 0 ) return 0;
            try {
                for (Future<Integer> task: taskList){
                    sumNumber +=  task.get();
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
            return sumNumber;
        }
    }

    public static void main(String[] args) {

        List<JavaBean> list = new CopyOnWriteArrayList<JavaBean>();
        list = Arrays.asList(
                new JavaBean(1l,"","",18,"[email protected]"),
                new JavaBean(1l,"","",19,"[email protected]"),
                new JavaBean(1l,"","",20,"[email protected]"),
                new JavaBean(1l,"","",21,"[email protected]"),
                new JavaBean(1l,"","",22,"[email protected]"),
                new JavaBean(1l,"","",23,"[email protected]"),
                new JavaBean(1l,"","",24,"[email protected]")
                );


        // TODO Auto-generated method stub
        MultithreadingListSum.ShareData shareData = new MultithreadingListSum.ShareData();
        int sum = shareData.getDataSum(list,2);
        System.out.println("最終運行的結果:"+sum);

    }
}