线程池复用原理

以你之姓@ 2022-10-28 03:43 142阅读 0赞

**线程池复用原理的业务背景**

**  **线程池使用固定数量的线程去执行不定量的任务，面对这种情况线程池通过 何种设计思想 以及编码实现此业务场景呢

**线程池复用设计思想**

**   **如何保证一个线程一直处于 Runable 状态 ，这里面得Runable状态会对应操作系统线程状态中的两种状态，分别是 Running 和 Ready，也就是说，Java 中处于 Runnable 状态的线程有可能正在执行，也有可能没有正在执行，正在等待被分配 CPU 资源。

细心观察，自旋锁，阻塞队列，这些都采用了一种设计思想，循环的设计思想来让线程保持这种状态

**线程池复用源码实现**

runWorker方法是线程执行的实际代码，其它无关的可以先过滤，注意导里面的循环了吧

final void runWorker(Worker w) {
            Thread wt = Thread.currentThread();
            Runnable task = w.firstTask;
            w.firstTask = null;
            w.unlock(); // allow interrupts
            boolean completedAbruptly = true;
            try {
                while (task != null || (task = getTask()) != null) {
                    w.lock();
                    // If pool is stopping, ensure thread is interrupted;
                    // if not, ensure thread is not interrupted.  This
                    // requires a recheck in second case to deal with
                    // shutdownNow race while clearing interrupt
                    if ((runStateAtLeast(ctl.get(), STOP) ||
                         (Thread.interrupted() &&
                          runStateAtLeast(ctl.get(), STOP))) &&
                        !wt.isInterrupted())
                        wt.interrupt();
                    try {
                        beforeExecute(wt, task);
                        Throwable thrown = null;
                        try {
                            task.run();
                        } catch (RuntimeException x) {
                            thrown = x; throw x;
                        } catch (Error x) {
                            thrown = x; throw x;
                        } catch (Throwable x) {
                            thrown = x; throw new Error(x);
                        } finally {
                            afterExecute(task, thrown);
                        }
                    } finally {
                        task = null;
                        w.completedTasks++;
                        w.unlock();
                    }
                }
                completedAbruptly = false;
            } finally {
                processWorkerExit(w, completedAbruptly);
            }
        }