package com.test.wyl;

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{
        int 
 
count = 300;                   //一個執行緒處理300條資料
int listSize = list.size();        //資料集合大小
int runSize = (listSize/count)+1;  //開啟的執行緒數
List<String> newlist = null;       //存放每個執行緒的執行資料
ExecutorService executor = Executors.newFixedThreadPool(runSize);      //建立一個執行緒池，數量和開啟執行緒的數量一樣
        //建立兩個個計數器
CountDownLatch begin = new 
 
CountDownLatch(1);
        CountDownLatch end = new CountDownLatch(runSize);
        //迴圈建立執行緒
for (int i = 0; i < runSize ; i++) {
        //計算每個執行緒執行的資料
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);
            }
            //執行緒類
MyThread mythead = new MyThread(newlist,begin,end);
            //這裡執行執行緒的方式是呼叫執行緒池裡的executor.execute(mythead)方法。
executor.execute(mythead);
        }

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

        //執行完關閉執行緒池
executor.shutdown();
    }



    //測試
public static void main(String[] args) {
        List<String> list = new ArrayList<String>();
      //資料越大執行緒越多
for (int i = 0; i < 3000000; i++) {
            list.add("hello"+i);
        }
        try {
            exec(list);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

package com.test.wyl;

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

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

    //建立個建構函式初始化 list,和其他用到的引數
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++) {
                //這裡還要說一下，，由於在實質專案中，當處理的資料存在等待超時和出錯會使執行緒一直處於等待狀態
                //這裡只是處理簡單的，
               //分批 批量插入
}

                //執行完讓執行緒直接進入等待
begin.await();
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
e.printStackTrace();
        } finally {
            //這裡要主要了，當一個執行緒執行完 了計數要減一不然這個執行緒會被一直掛起
            // ，end.countDown()，這個方法就是直接把計數器減一的
end.countDown();
        }
    }


}