多线程处理list集合

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多线程处理list集合

import lombok.SneakyThrows;
import java.util.*;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
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/**
 * 模拟处理考试分值计算场景
 *
 * @author lyn
 * @date 2022/2/22 16:20
 */
public class TestThreadPool {
    private static volatile AtomicInteger index = new AtomicInteger(0);
    ;
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    public static void main(String[] args) {
        //准备基础数据
        final int totalSize = 10045;
        Random r = new Random();
        List<StuScore> list = new ArrayList<>();
        for (int i = 1; i <= totalSize; i++) {
            list.add(new StuScore(i, r.nextInt(55) + 40, r.nextInt(55) + 40, r.nextInt(55) + 40, 0));
        }
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        //多线程计算成绩
        List<StuScore> result = partJob(list);
        //取总分前五名展示
        List<StuScore> collect = result.stream().sorted(Comparator.comparing(StuScore::getTotalScore).reversed()).limit(5).collect(Collectors.toList());
        for (StuScore stuScore : collect) {
            System.out.println(stuScore);
        }
       
        System.out.println(index);
    }
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    @SneakyThrows
    private static List<StuScore> partJob(List<StuScore> list) {
        //子集合的大小
        final int sonSize = 500;
        //分割的份数
        int parts = (list.size() + sonSize - 1) / sonSize;
        //存放异步处理后结果数据
        List<StuScore> resultList = Collections.synchronizedList(new ArrayList<>());
        ExecutorService executorService = Executors.newFixedThreadPool(5);
        CountDownLatch countDownLatch = new CountDownLatch(parts);
        //分割集合
        List<List<StuScore>> partsList = IntStream.range(0, parts).boxed().parallel().map(i -> {
            int fromIndex = i * sonSize;
            long toIndex = sonSize;
            if (i + 1 == list.size()) {
                toIndex = list.size() - fromIndex;
            }
            return list.stream().skip(fromIndex).limit(toIndex).collect(Collectors.toList());
        }).collect(Collectors.toList());
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        for (int i = 0; i < partsList.size(); i++) {
            List<StuScore> sonScoreList = partsList.get(i);
　　　　　　　//处理数据
            executorService.execute(new PartDisPose(i, sonScoreList, resultList, countDownLatch));
        }
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        // 等待所有线程执行完毕
        countDownLatch.await();
        executorService.shutdown();
        return resultList;
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    }
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    /**
     * 分片处理内部类
     */
    private static class PartDisPose implements Runnable {
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        private int count;
        private List<StuScore> sonList;
        private List<StuScore> resultList;
        private CountDownLatch countDownLatch;
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        private PartDisPose(int count, List<StuScore> sonList, List<StuScore> resultList, CountDownLatch countDownLatch) {
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            this.count = count;
            this.sonList = sonList;
            this.resultList = resultList;
            this.countDownLatch = countDownLatch;
        }
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        @Override
        public void run() {
            for (StuScore stu : sonList) {
                stu.setTotalScore(stu.getChinese() + stu.getEnglish() + stu.getMath());
                index.incrementAndGet();
            }
            resultList.addAll(sonList);
            System.out.println("count: " + count + ",sonListSize: " + sonList.size());
            countDownLatch.countDown();
        }
    }
}

学生分数实体类

@Data
@AllArgsConstructor
@NoArgsConstructor
public class StuScore {
   private int id;
   private int math;
   private int english;
   private int chinese;
   private int totalScore;
}
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