Java线程池详解 - ThreadPoolExecutor

Android中经常出现一些任务不执行重新进入或杀掉进程又可以执行为什么要充分理解拒绝策略当线程池中的线程已满究竟是抛出异常try-catch还是丢弃任务还是其他的方法处理拒绝策略执行的条件线程池中的线程数量 最大线程数 任务队列如果任务队列的数量设置很大时间设置很长也没啥意义。比如设置100个1分钟。有些任务可能等待非常久才执行。ThreadPoolExecutor(int corePoolSize,int maximumPoolSize,long keepAliveTime,TimeUnit unit,BlockingQueueRunnable workQueue,ThreadFactory threadFactory,RejectedExecutionHandler handler)int corePoolSize, // 核心线程数定义线程池中始终保持存活的线程数量即使这些线程处于空闲状态。除非设置allowCoreThreadTimeOutexecutor.allowCoreThreadTimeOut(true); // 允许核心线程超时销毁int maximumPoolSize, // 最大线程数定义线程池允许创建的最大线程数量包括核心线程和非核心线程。long keepAliveTime, // 空闲线程存活时间定义当线程池中的线程数量超过corePoolSize 时多余的空闲线程在终止前等待新任务的最长时间。TimeUnit unit, // 时间单位BlockingQueueRunnable workQueue, // 任务队列定义用于保存等待执行的任务的阻塞队列。任务缓冲区核心作用是在线程资源有限时暂存待执行任务平衡任务提交速度与线程处理能力。SynchronousQueue同步移交队列LinkedBlockingQueue无界/有界队列ArrayBlockingQueue有界队列PriorityBlockingQueue优先级队列DelayQueue延迟队列ThreadFactory threadFactory, // 线程工厂用于创建新线程的工厂类。RejectedExecutionHandler handler // 拒绝策略定义当线程池和队列都满了无法处理新任务时的处理策略。内置拒绝策略AbortPolicy默认抛出RejectedExecutionExceptionCallerRunsPolicy调用者线程执行 - 可能会在主线程中执行耗时任务可能会奔溃DiscardPolicy静默丢弃DiscardOldestPolicy丢弃队列中最旧的任务线程数变化示意图任务提交 → 当前线程数 corePoolSize → 创建新线程任务提交 → 当前线程数 corePoolSize → 任务入队任务提交 → 队列已满 当前线程数 maximumPoolSize → 创建新线程任务提交 → 队列已满 当前线程数 maximumPoolSize → 执行拒绝策略这个例子创建多个线程池如果第1个满了使用第2个如果又满了就使用新的线程执行。/** * Author : wn * Email : maoning20080809163.com * Date : 2025/12/21 12:28 * Description : 测试线程池 */ public classThreadPoolMainActivityextends AppCompatActivity implements View.OnClickListener{ Override protected void onCreate(Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.thread_pool_main); findViewById(R.id.thread_pool_btn1).setOnClickListener(this); findViewById(R.id.thread_pool_btn2).setOnClickListener(this); findViewById(R.id.thread_pool_btn3).setOnClickListener(this); findViewById(R.id.thread_pool_btn4).setOnClickListener(this); } Override public void onClick(View v) { if(v.getId() R.id.thread_pool_btn1){ ThreadPoolExecutorHelper.test1(); } else if(v.getId() R.id.thread_pool_btn2){ ThreadPoolExecutorHelper.test2(); } else if(v.getId() R.id.thread_pool_btn3){ThreadPoolExecutorAutoHelper.test3();} else if(v.getId() R.id.thread_pool_btn4){ThreadPoolExecutorAutoHelper.test4();} } }/** * Author : wn * Email : maoning20080809163.com * Date : 2025/12/21 17:10 * Description : */ public classThreadPoolExecutorAutoHelper{ //线程池自动切换 线程最大数(核心非核心线程)等待队列都用完才异常。 public static void test3(){ ThreadPoolExecutor cpuExecutor ThreadPoolExecutorAuto.getCpuExecutor(); //ThreadPoolMonitor threadPoolMonitor new ThreadPoolMonitor(cpuExecutor); for(int i 0; i 50; i){ ThreadTask3 threadTask3 new ThreadTask3(ThreadTask3 i i); try { cpuExecutor.execute(threadTask3); LogUtils.Companion.i(ThreadPoolExecutorHelper.TAG, ThreadPoolExecutorHelper test3() i i); } catch (RejectedExecutionException e){ try { //cpu线程池异常 , 使用io线程池 线程最大数等待队列 LogUtils.Companion.w(ThreadPoolExecutorHelper.TAG, ThreadPoolExecutorAutoHelper test3() cpu RejectedExecutionException e e.getMessage()); ThreadPoolExecutor ioExecutor ThreadPoolExecutorAuto.getIoExecutor(); ioExecutor.execute(threadTask3); } catch (RejectedExecutionException e1){ //io线程池也异常 LogUtils.Companion.e(ThreadPoolExecutorHelper.TAG, ThreadPoolExecutorAutoHelper test3() io RejectedExecutionException e e.getMessage()); //使用新的Thread执行或者想想其他的扩展实现 一定要使用start() new Thread(threadTask3, cpu-io all exception).start(); } } } } //先调用test3测试线程池满了以后使用子线程。再用比较少的线程看看线程池能否正常执行 public static void test4(){ ThreadPoolExecutor cpuExecutor ThreadPoolExecutorAuto.getCpuExecutor(); //ThreadPoolMonitor threadPoolMonitor new ThreadPoolMonitor(cpuExecutor); for(int i 0; i 3; i){ ThreadTask3 threadTask3 new ThreadTask3(ThreadTask3 i i); try { cpuExecutor.execute(threadTask3); LogUtils.Companion.i(ThreadPoolExecutorHelper.TAG, ThreadPoolExecutorHelper test4() i i); } catch (RejectedExecutionException e){ try { //cpu线程池异常 , 使用io线程池 线程最大数等待队列 LogUtils.Companion.w(ThreadPoolExecutorHelper.TAG, ThreadPoolExecutorAutoHelper test4() cpu RejectedExecutionException e e.getMessage()); ThreadPoolExecutor ioExecutor ThreadPoolExecutorAuto.getIoExecutor(); ioExecutor.execute(threadTask3); } catch (RejectedExecutionException e1){ //io线程池也异常 LogUtils.Companion.e(ThreadPoolExecutorHelper.TAG, ThreadPoolExecutorAutoHelper test4() io RejectedExecutionException e e.getMessage()); //使用新的Thread执行或者想想其他的扩展实现 一定要使用start() new Thread(threadTask3, cpu-io all exception).start(); } } } } }/** * Author : wn * Email : maoning20080809163.com * Date : 2025/12/21 15:17 * Description : 多线程池自动切换如果cpu线程池满了自动切换到io线程池 */ public classThreadPoolExecutorAuto{//CPU密集型线程池 private static ThreadPoolExecutor cpuExecutor; //IO密集型任务池 private static ThreadPoolExecutor ioExecutor;//单线程顺序执行池 private static ThreadPoolExecutor serialExecutor; static { //线程数 int cpuCount Runtime.getRuntime().availableProcessors(); //int cpuCount 2; LogUtils.Companion.i(ThreadPoolExecutorHelper.TAG, ThreadPoolExecutorManager cpuCount cpuCount); //CPU密集型处理图像计算等 cpuExecutor new ThreadPoolExecutor( cpuCount, cpuCount 1, 3L, TimeUnit.SECONDS, new LinkedBlockingQueue(10), //队列也不能太多会导致等待时间太久。 new CustomThreadFactory(ThreadPoolExecutorAuto my-cpu-pool, Thread.MAX_PRIORITY - 1), new ThreadPoolExecutor.AbortPolicy() //抛出异常策略 ); //IO密集型网络请求、文件读写 ioExecutor new ThreadPoolExecutor( cpuCount * 2, cpuCount * 3, 6L, TimeUnit.SECONDS, new LinkedBlockingQueue(20), new CustomThreadFactory(ThreadPoolExecutorAuto my-io-pool, Thread.NORM_PRIORITY), new ThreadPoolExecutor.AbortPolicy() //抛出异常测试了 ); //串行执行数据库操作等需要顺序执行的任务 serialExecutor new ThreadPoolExecutor( 1, 1, 0L, TimeUnit.SECONDS, new LinkedBlockingQueue(), new CustomThreadFactory(ThreadPoolExecutorAuto my-serial-pool, Thread.NORM_PRIORITY) ); //防止内存泄漏监听应用生命周期 Application application MyApp.myApp; application.registerActivityLifecycleCallbacks(new Application.ActivityLifecycleCallbacks() { Override public void onActivityCreated(NonNull Activity activity, Nullable Bundle savedInstanceState) { } Override public void onActivityStarted(NonNull Activity activity) { } Override public void onActivityResumed(NonNull Activity activity) { } Override public void onActivityPaused(NonNull Activity activity) { } Override public void onActivityStopped(NonNull Activity activity) { } Override public void onActivitySaveInstanceState(NonNull Activity activity, NonNull Bundle outState) { } Override public void onActivityDestroyed(NonNull Activity activity) { //清理与Activity相关的任务 LogUtils.Companion.i(ThreadPoolExecutorHelper.TAG, 清理与Activity相关的任务 ThreadPoolExecutorManager onActivityDestroyed activity); } }); } //CPU密集型线程池 public static ThreadPoolExecutor getCpuExecutor(){ return cpuExecutor; } //IO密集型任务池 public static ThreadPoolExecutor getIoExecutor(){ return ioExecutor; } //单线程顺序执行池 public static ThreadPoolExecutor getSerialExecutor(){ return serialExecutor; } }/** * Author : wn * Email : maoning20080809163.com * Date : 2025/12/21 15:50 * Description : */ public classThreadTask3implements Runnable{ //private static final String TAG ThreadTask2; private String threadTaskName; public ThreadTask3(String name){ this.threadTaskName name; } private static int taskCount 1; Override public void run() { try { Thread.sleep(100); LogUtils.Companion.i(ThreadPoolExecutorHelper.TAG, ThreadTask3 执行任务taskCount taskCount isMain isMainThread() , threadTaskName , Thread.currentThread().getName() , Thread.currentThread().getId() , this.getClass()); taskCount ; //这里执行的是子线程 如果使用handler刷新必须指定在主线程中执行Looper.getMainLooper() /*new Handler(Looper.getMainLooper()).post(() - { //LogUtils.Companion.i(TAG, ThreadTask2 执行任务 Thread.currentThread().getName() , Thread.currentThread().getId()); });*/ } catch (Exception e){ e.printStackTrace(); } } public boolean isMainThread() { // 方法1比较当前线程和主线程的线程对象 return Looper.myLooper() Looper.getMainLooper(); //return Looper.getMainLooper().getThread() Thread.currentThread(); } }/** * Author : wn * Email : maoning20080809163.com * Date : 2025/12/21 15:37 * Description : 线程池监控 */ public classThreadPoolMonitor{ private ThreadPoolExecutor executor; private ScheduledExecutorService monitor; public ThreadPoolMonitor(ThreadPoolExecutor executor){ this.executor executor; //启动监控 monitor Executors.newSingleThreadScheduledExecutor(); monitor.scheduleAtFixedRate(this::reportStatus, 0, 5, TimeUnit.SECONDS); } private void reportStatus(){ LogUtils.Companion.d(ThreadPoolExecutorHelper.TAG, ThreadPoolMonitor reportStatus());StringBuilder sb new StringBuilder(); sb.append(ThreadPoolMonitor reportStatus() ); sb.append( , Pool Size : executor.getPoolSize()); sb.append( , Max Pool Size : executor.getMaximumPoolSize()); sb.append( , Core Pool Size : executor.getCorePoolSize()); sb.append( , Active Threads : executor.getActiveCount()); sb.append( , Queue Size : executor.getQueue().size()); sb.append( , Completed Tasks : executor.getCompletedTaskCount()); sb.append( , Largest Pool Size : executor.getLargestPoolSize()); LogUtils.Companion.i(ThreadPoolExecutorHelper.TAG, sb.toString());//动态调整如果队列长期满载增加核心线程数 - 可以灵活配置 if(executor.getQueue().size() 80){ executor.setCorePoolSize(Math.min(executor.getCorePoolSize() 2, executor.getMaximumPoolSize())); } } public void shutdown(){ executor.shutdown(); monitor.shutdown(); } }thread_pool_main.xml布局?xml version1.0 encodingutf-8? androidx.constraintlayout.widget.ConstraintLayout android:layout_widthmatch_parent android:layout_heightmatch_parent xmlns:androidhttp://schemas.android.com/apk/res/android xmlns:apphttp://schemas.android.com/apk/res-auto xmlns:toolshttp://schemas.android.com/tools androidx.appcompat.widget.AppCompatTextView android:idid/thread_pool_title android:layout_widthwrap_content android:layout_heightwrap_content app:layout_constraintTop_toTopOfparent app:layout_constraintStart_toStartOfparent app:layout_constraintEnd_toEndOfparent android:layout_marginTop20dp android:textSize30sp android:textColorcolor/black android:text测试线程池/ androidx.appcompat.widget.AppCompatButton android:idid/thread_pool_btn1 android:layout_widthwrap_content android:layout_heightwrap_content app:layout_constraintStart_toStartOfparent app:layout_constraintTop_toBottomOfid/thread_pool_title android:text测试线程池满抛出异常/ androidx.appcompat.widget.AppCompatButton android:idid/thread_pool_btn2 android:layout_widthwrap_content android:layout_heightwrap_content app:layout_constraintStart_toStartOfparent app:layout_constraintTop_toBottomOfid/thread_pool_btn1 android:textColorcolor/red android:text测试线程池状态/ androidx.appcompat.widget.AppCompatButton android:idid/thread_pool_btn3 android:layout_widthwrap_content android:layout_heightwrap_content app:layout_constraintStart_toStartOfparent app:layout_constraintTop_toBottomOfid/thread_pool_btn2 android:textColorcolor/blue android:text测试线程池自动切换设计 - 非常多线程同时执行/ androidx.appcompat.widget.AppCompatButton android:idid/thread_pool_btn4 android:layout_widthwrap_content android:layout_heightwrap_content app:layout_constraintStart_toStartOfparent app:layout_constraintTop_toBottomOfid/thread_pool_btn3 android:textColorcolor/blue android:text测试线程池自动切换设计 - 少量线程执行/ /androidx.constraintlayout.widget.ConstraintLayout