線程池中利用多線程大量插入數據

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import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class test {


    public static void exec(List<String> list) throws InterruptedException {
        //一個線程處理300條數據
        int count = 300;
        //數據集合大小
        int listSize = list.size();
        //開啟的線程數
        int runSize =  listSize%count > 0 ?  ((listSize/count)+1) : (listSize/count);
        //存放每個線程的執行數據
        List<String> newlist = null;
        //創建一個線程池，數量和開啟線程的數量一樣
        ExecutorService executor = Executors.newFixedThreadPool(runSize);
        //創建兩個個計數器
        CountDownLatch begin = new CountDownLatch(1);
        CountDownLatch end = new CountDownLatch(runSize);
        //循環創建線程
        for (int i = 0; i < runSize; i++) {
            //計算每個線程執行的數據
            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);
            }
            //線程類
            MyThread mythead = new MyThread(newlist, begin, end);
            //這里執行線程的方式是調用線程池里的executor.execute(mythead)方法。
            executor.execute(mythead);
        }

        begin.countDown();
        end.await();

        //執行完關閉線程池
        executor.shutdown();
    }


    //測試
    public static void main(String[] args) {
        List<String> list = new ArrayList<String>();
        //數據越大線程越多
        for (int i = 0; i < 3000000; i++) {
            list.add("hello" + i);
        }
        try {
            exec(list);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

import java.util.List;
import java.util.concurrent.CountDownLatch;

public class MyThread implements Runnable {
    private List<String> list;
    private CountDownLatch begin;
    private CountDownLatch end;

    //創建個構造函數初始化 list,和其他用到的參數
    public MyThread(List<String> list, CountDownLatch begin, CountDownLatch end) {
        this.list = list;
        this.begin = begin;
        this.end = end;
    }

    @Override
    public void run() {
        try {
            for (int i = 0; i < list.size(); i++) {
                //這里還要說一下，由於在實質項目中，當處理的數據存在等待超時和出錯會使線程一直處於等待狀態
                //這里只是處理簡單的，
                //分批 批量插入
            }

            //執行完讓線程直接進入等待
            begin.await();
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {
            //這里要注意了，當一個線程執行完了計數要減一，不然這個線程會被一直掛起
            // end.countDown()，這個方法就是直接把計數器減一的
            end.countDown();
        }
    }

}