java多线程分段并行处理liat集合数据

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.*;

public class test4_thread4 {

    public static void main(String[] args)  {
        List<String> list = new ArrayList<String>();

        for (int i = 1; i <= 5; i++) {
            list.add(i + "");
        }
        long l = System.currentTimeMillis();
        new test4_thread4().importData(list,5);
        System.out.println(System.currentTimeMillis()-l);
    }
    public void importData(List list,int count) {
        //分count一组
        int listsize = list.size();
        //线程数
        int RunSize = (listsize / count) + 1;
        ThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(RunSize);
        CountDownLatch countDownLatch = new CountDownLatch(RunSize);
        for (int i = 0; i < RunSize; i++) {
            List newList = null;
            if ((i + 1) == RunSize) {
                int startIndex = (i * count);
                int endIndex = list.size();
                newList = list.subList(startIndex, endIndex);
            } else {
                int startIndex = i * count;
                int endIndex = (i + 1) * count;
                newList = list.subList(startIndex, endIndex);
            }
            ImportTask task = new ImportTask(newList, countDownLatch);
            executor.execute(task);
        }
        try {
            countDownLatch.await();//主线程等待所有线程完成任务
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        // 所有线程完威任务后的一些业务
        System.out.println("完成! ");
        executor.shutdown();
    }
     class ImportTask implements Runnable{
        private List list;
        private CountDownLatch countDownLatch;
         ImportTask(List newList,CountDownLatch countDownLatch){
            this.list = newList;
            this.countDownLatch = countDownLatch;
         }
         @Override
         public void run() {
             int size = list.size();
             if (size > 0){
                for (int i = 0; i < size; i++) {
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }

                System.out.println(list.size());
            }
            countDownLatch.countDown();
         }
     }
}