两种多线程查库写法

可以用于excel导出场景

直接上代码：

package com.threadmore;import java.util.ArrayList;import java.util.List;import java.util.concurrent.ArrayBlockingQueue;import java.util.concurrent.CountDownLatch;import java.util.concurrent.ThreadPoolExecutor;import java.util.concurrent.TimeUnit;public class MutiThreadQuery {    public List<Object> queryMethedOne() {        ThreadPoolExecutor executor =                 new ThreadPoolExecutor(5, 10, 1, TimeUnit.MINUTES,                         new ArrayBlockingQueue<Runnable>(10),                         new ThreadPoolExecutor.CallerRunsPolicy());        System.out.println("start thread pool...");        List<Object> resultList = new ArrayList<Object>();        //查询页数（批次）        int pageIndex = 0;        int n = 30;//当页数小于n（总线程数）时，跳出        do {            MergeRunnable mr = new MergeRunnable(resultList, pageIndex);            executor.execute(mr);            System.out.println("pageIndex:"+pageIndex);            pageIndex++;        }while(pageIndex < n);//当页数小于n（总线程数）时，跳出        executor.shutdown();//不能再提交新任务        boolean loop = true;        try {            do {//等待所有任务完成                System.out.println("线程池中线程数目:" + executor.getPoolSize());                System.out.println("队列中等待执行的任务数目:" +  executor.getQueue().size());                System.out.println("已执行完的任务数目:" + executor.getCompletedTaskCount());                System.out.println("当前的resultList数量:" + resultList.size());                System.out.println("总共记录数:" + "xxx");                //阻塞，直到线程池所有的任务结束，2秒判断一次                loop = !executor.awaitTermination(2, TimeUnit.SECONDS);            }while(loop);        } catch (InterruptedException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }        return resultList;    }    class MergeRunnable implements Runnable{        private List<Object> allRest;        private int pageIndex;        public MergeRunnable(List<Object> resultList, int pageIndex) {            this.allRest = resultList;            this.pageIndex = pageIndex;        }        @Override        public void run() {            System.err.println(Thread.currentThread().getName() +" query data start...");            List<Object> tempPageRest = queryFromDataBase(pageIndex);            synchronized(allRest) {                allRest.addAll(tempPageRest);            }            System.err.println(Thread.currentThread().getName() +" query data end...");        }    }    private List<Object> queryFromDataBase(int pageIndex) {        // TODO do some operation from database        try {            Thread.sleep(10*1000);        } catch (InterruptedException e) {            e.printStackTrace();        }        List<Object> test = new ArrayList<Object>();        return test;    }    //----------------------------华丽的分割线----以下是第二种写法，为了测试和第一种有没有性能上的差别---------    public List<Object> queryMethedTwo() {        ThreadPoolExecutor executor =                 new ThreadPoolExecutor(5, 10, 1, TimeUnit.MINUTES,                         new ArrayBlockingQueue<Runnable>(10),                         new ThreadPoolExecutor.CallerRunsPolicy());        System.out.println("start thread pool...");        List<Object> resultList = new ArrayList<Object>();        //查询页数（批次）        int pageIndex = 0;        int n = 30;//当页数小于n（总线程数）时，跳出        CountDownLatch latch = new CountDownLatch(n);        for (int i = 0; i < n; i++) {            MergeRunnable1 mr1 = new MergeRunnable1(resultList, pageIndex, latch);            executor.execute(mr1);            System.out.println("pageIndex:"+pageIndex);            pageIndex++;        }        executor.shutdown();        try {            latch.await(2,TimeUnit.MINUTES);        } catch (InterruptedException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }        return resultList;    }    class MergeRunnable1 implements Runnable{        private List<Object> allRest;        private int pageIndex;        private CountDownLatch latch;        public MergeRunnable1(List<Object> resultList, int pageIndex, CountDownLatch latch) {            this.allRest = resultList;            this.pageIndex = pageIndex;            this.latch = latch;        }        @Override        public void run() {            System.err.println(Thread.currentThread().getName() +" query data start...");            List<Object> tempPageRest = queryFromDataBase(pageIndex);            synchronized(allRest) {                allRest.addAll(tempPageRest);            }            latch.countDown();            System.err.println(Thread.currentThread().getName() +" query data end...");        }    }    //----------------------------华丽的分割线----以下是第二种写法，为了测试和第一种有没有性能上的差别---------    public static void main(String[] args) {        MutiThreadQuery m = new MutiThreadQuery();        long a = System.currentTimeMillis();        m.queryMethedOne();//      m.queryMethedTwo();        System.out.println("#################:"+(System.currentTimeMillis() - a)+"ms");    }}

之后一篇主要分析多线程包中API使用细节。