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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 list) throws InterruptedException {
//一个线程处理300条数据
int count = 300;
//数据集合大小
int listSize = list.size();
//开启的线程数
int runSize = listSize%count > 0 ? ((listSize/count)+1) : (listSize/count);
//存放每个线程的执行数据
List newlist = null;
//创建一个线程池，数量和开启线程的数量一样
ExecutorService executor = Executors.newFixedThreadPool(runSize);
//创建两个个计数器
CountDownLatch begin = new CountDownLatch(1);
CountDownLatch end = new CountDownLatch(runSize);
//循环创建线程
for (int i = 0; i < runSize; i++) {
//计算每个线程执行的数据
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);
}
//线程类
MyThread mythead = new MyThread(newlist, begin, end);
//这里执行线程的方式是调用线程池里的executor.execute(mythead)方法。
executor.execute(mythead);
}
begin.countDown();
end.await();
//执行完关闭线程池
executor.shutdown();
}
//测试
public static void main(String[] args) {
List list = new ArrayList();
//数据越大线程越多
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 list;
private CountDownLatch begin;
private CountDownLatch end;
//创建个构造函数初始化 list,和其他用到的参数
public MyThread(List 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++) {
//这里还要说一下，由于在实质项目中，当处理的数据存在等待超时和出错会使线程一直处于等待状态
//这里只是处理简单的，
//分批 批量插入
}
//执行完让线程直接进入等待
begin.await();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
//这里要注意了，当一个线程执行完了计数要减一，不然这个线程会被一直挂起
// end.countDown()，这个方法就是直接把计数器减一的
end.countDown();
}
}
}
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