ThreadPoolExecutor
ThreadPoolExecutor线程池，java提供开发框架，管理线程的创建、销毁、优化、监控等。
有4种不同的任务队列:
- ArrayBlockingQueue：基于数组结构的任务队列。此队列按先进先出的原则对任务进行排序。
- LinkedBlockingQueue：基于链表结构的任务队列。此队列也是按先进先出的原则对任务进行排序。但性能比ArrayBlockingQueue高。
- synchronousQueue：不存储元素的任务队列。每个插入操作必须等到另一个线程调用移除操作，否则插入操作一直处于阻塞状态。
- PriorityBlockingQueue：具有优先级的任务队列。此队列中的元素必须能够比较。
拒绝策略：
RejectedExecutionHandler（饱和策略 ）：当线程池中的线程数大于maximumPoolSize时，线程池就不能在处理任何任务了，这时线程池会抛出异常。原因就是这个策略默认情况下是AbortPolicy：表示无法处理新任务时抛出异常。
- AbortPolicy：直接抛出异常。
- CallerRunsPolicy：只用调用者所在线程来运行任务。
- DiscardOldestPolicy：丢弃队列里最近的一个任务，并执行当前任务
- DiscardPolicy：不处理，丢弃掉。
自定义：
ThreadPoolExecutor.AbortPolicy()
//抛出java.util.concurrent.RejectedExecutionException异常
ThreadPoolExecutor.CallerRunsPolicy()
//重试添加当前的任务，他会自动重复调用execute()方法
ThreadPoolExecutor.DiscardOldestPolicy()
//抛弃旧的任务
ThreadPoolExecutor.DiscardPolicy()
// 抛弃当前的任务
private static class RecjectThreadHandler implements RejectedExecutionHandler
{
@Override
public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) {
}
// 异常记录
private void doLog(Runnable r, ThreadPoolExecutor executor)
{
System.out.println(r.toString()+"excutor failed."+executor.getCompletedTaskCount());
}
}
创建线程工厂：
用来创建线程。
public class CheckThreadFactory implements ThreadFactory
{
private String threadGroupName;
private AtomicInteger count = new AtomicInteger(0);
public CheckThreadFactory(String threadGroupName) {
this.threadGroupName = threadGroupName;
}
@Override
public Thread newThread(Runnable r)
{
Thread thread = new Thread(r);
thread.setName(threadGroupName+"--"+count.addAndGet(1));
thread.setPriority(5);
thread.setDaemon(true);.// 设置为守护线程， 默认为主线程
return thread;
}
}
线程工具类：
/**
* @author Donald
* @create 2019-09-21 21:40
*/
public class CheckExcetPool
{
// 线程池核心线程数
private static int corePoolSize = Runtime.getRuntime().availableProcessors() * 5;
// 最大线程数
private static int maximumPoolSize = corePoolSize > 255 ? 255 : corePoolSize * 2;
// 线程池中除了核心线程，其他线程的最大存活时间
private static int keepAliveTime = 60;
// 时间单位
private static TimeUnit timeUnit = TimeUnit.SECONDS;
// 线程等待队列
private static BlockingQueue queue = new LinkedBlockingQueue();
//private static BlockingQueue queue = new ArrayBlockingQueue<Runnable>(30);
// 创建线程的工厂
private static CheckThreadFactory checkThreadFactory = new CheckThreadFactory("checkGroup");
// 拒绝策略 当提交任务数超过maxmumPoolSize+workQueue之和时,
// * 即当提交第41个任务时(前面线程都没有执行完,此测试方法中用sleep(100)),
// * 任务会交给RejectedExecutionHandler来处理
/*handler的拒绝策略：
有四种：第一种AbortPolicy:不执行新任务，直接抛出异常，提示线程池已满
第二种DisCardPolicy:不执行新任务，也不抛出异常
第三种DisCardOldSetPolicy:将消息队列中的第一个任务替换为当前新进来的任务执行
第四种CallerRunsPolicy:直接调用execute来执行当前任务*/
private static ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(
corePoolSize,
maximumPoolSize,
keepAliveTime,
timeUnit,
queue,
checkThreadFactory
);
public static void submit( Runnable runnable)
{
System.out.println(corePoolSize+"::"+queue.size());
threadPoolExecutor.submit(runnable);
}
public static <T> Future submit(Callable<T> callable)
{
return threadPoolExecutor.submit(callable);
}
public static <T> void excutor( Runnable run, T result )
{
threadPoolExecutor.submit( run,result );
}
public static void excutor( Runnable run)
{
threadPoolExecutor.execute( run);
}
private static class RecjectThreadHandler implements RejectedExecutionHandler
{
@Override
public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) {
}
// 异常记录
private void doLog(Runnable r, ThreadPoolExecutor executor)
{
System.out.println(r.toString()+"excutor failed."+executor.getCompletedTaskCount());
}
}
}
线程服务类，实现runnable 接口：
/**
* @author Donald
* @create 2019-09-21 23:00
*/
public class ThreadService implements Runnable
{
private CountDownLatch countDownLatch;
private UserInterface userInterface;
public ThreadService(CountDownLatch countDownLatch, UserInterface userInterface) {
this.countDownLatch = countDownLatch;
this.userInterface = userInterface;
}
@Override
public void run()
{
try {
long start = System.currentTimeMillis();
userInterface.doSomething();
System.err.println(String.format("user time :%s",System.currentTimeMillis()-start));
Thread.sleep(1000);
}catch ( Exception e)
{
e.printStackTrace();
}finally {
countDownLatch.countDown();
}
}
}
具体业务逻辑：
/**
* @author Donald
* @create 2019-09-21 22:51
*/
public interface UserInterface
{
void doSomething();
}
业务类：
/**
* @author Donald
* @create 2019-09-21 22:51
*/
public class UserService implements UserInterface
{
private int number;
public UserService(int number) {
this.number = number;
}
@Override
public void doSomething() {
System.out.println(Thread.currentThread().getName()+"<<<<"+number);
}
}