J.U.C--扩展ThreadPoolExecutor

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ThreadPoolExecutor是可以扩展的，它提供了几个在子类中改写的方法，比如：beforeExecute()、afterExecute()、和terminated()方法。这些方法可以扩展ThreadPoolExecutor的执行行为。比如剪监控线程池或则是添加日志之类的。

下面是一个例子，给线程池添加统计信息：

package thread;import org.apache.log4j.Logger;import java.util.concurrent.*;import java.util.concurrent.atomic.AtomicLong;/** * Created by louyuting on 17/1/12. */public class TimingThreadPool extends ThreadPoolExecutor{    public TimingThreadPool(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue) {        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue);    }    public TimingThreadPool(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, RejectedExecutionHandler handler) {        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, handler);    }    public TimingThreadPool(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory) {        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory);    }    public TimingThreadPool(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory, RejectedExecutionHandler handler) {        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory, handler);    }    private final ThreadLocal<Long> startTime = new ThreadLocal<Long>();    private final Logger log = Logger.getLogger("TimingThreadPool");    private final AtomicLong numTasks = new AtomicLong();    private final AtomicLong totalTime = new AtomicLong();    @Override    protected void beforeExecute(Thread t, Runnable r) {        super.beforeExecute(t, r);        System.out.println(String.format("Thread %s: start %s", t, r));        startTime.set(System.nanoTime());    }    @Override    protected void afterExecute(Runnable r, Throwable t) {        try {            long endTime = System.nanoTime();            long taskTime = endTime-startTime.get();            numTasks.incrementAndGet();            totalTime.addAndGet(taskTime);            System.out.println(String.format("Thread %s end %s time=%dns", t,r,taskTime));        } finally {            super.afterExecute(r,t);        }    }    @Override    protected void terminated() {        super.terminated();    }    public static void main(String[] args) {        TimingThreadPool t = new TimingThreadPool(1,1,0L, TimeUnit.MILLISECONDS,                new LinkedBlockingQueue<Runnable>());        for(int i=0; i<3; i++){            t.submit(new Runnable() {                @Override                public void run() {                    System.out.println("test");                }            });        }        t.shutdown();    }}

运行结果如下
output

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