#### 線程異常處理 * 在run方法上增加異常處理 ``` new Thread(() -> { try { System.err.println(3 / 2); System.err.println(3 / 0); } catch (Exception e) { System.err.println("Catch exception===>" + e.getMessage()); } }).start(); ``` * 使用UncaughtExceptionHandler處理未捕獲異常 ``` Thread thread = new Thread(() -> { System.err.println(3 / 2); System.err.println(3 / 0); }); thread.setUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() { @Override public void uncaughtException(Thread t, Throwable e) { System.err.println(Thread.currentThread().getName() + "==>" + e.getMessage()); } }); thread.start(); ``` 可以為所有的Thread設置一個默認的UncaughtExceptionHandler，通過調用Thread.setDefaultUncaughtExceptionHandler\(Thread.UncaughtExceptionHandler eh\)方法 ``` public static void main(String[] args) throws InterruptedException { Thread.setDefaultUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() { @Override public void uncaughtException(Thread t, Throwable e) { System.err.println("全局線程默認異常處理：" + t.getName() + "\n" + e.getMessage()); } }); new Thread(() -> { System.err.println(3 / 0); }).start(); new Thread(() -> { System.err.println(args[4]); }).start(); } ``` #### 線程池異常處理 ExecutorService-&gt;execute方法線程處理 ``` public class ExecuteCaught { public static void main(String[] args) { ExecutorService exec = Executors.newCachedThreadPool(); Thread thread = new Thread(new Task()); thread.setUncaughtExceptionHandler(new ExceptionHandler()); exec.execute(thread); exec.shutdown(); } } output=====> 1 Exception in thread "pool-1-thread-1" java.lang.ArithmeticException: / by zero at com.exception.Task.run(NoCaughtThread.java:25) at java.lang.Thread.run(Unknown Source) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at java.lang.Thread.run(Unknown Source) ``` 該方式并未捕獲異常，正確的處理方法 ``` public class ExecuteCaught { public static void main(String[] args) { ExecutorService exec = Executors.newCachedThreadPool(); exec.execute(new ThreadPoolTask()); exec.shutdown(); } } class ThreadPoolTask implements Runnable { @Override public void run() { Thread.currentThread().setUncaughtExceptionHandler(new ExceptionHandler()); System.out.println(3/2); System.out.println(3/0); System.out.println(3/1); } } ``` _注意_ 只有通過execute提交的任務，才能將它拋出的異常交給UncaughtExceptionHandler，而通過submit提交的任務，無論是拋出的未檢測異常還是已檢查異常，都將被認為是任務返回狀態的一部分。如果一個由submit提交的任務由于拋出了異常而結束，那么這個異常將被Future.get封裝在ExecutionException中重新拋出 ``` public static void main(String[] args) throws InterruptedException { ExecutorService exec = Executors.newCachedThreadPool(); exec.submit(() -> { System.err.println(3 / 0); }); exec.shutdown(); } ### 未捕獲異常 ``` 正確方式： ``` public static void main(String[] args) throws InterruptedException { ExecutorService exec = Executors.newCachedThreadPool(); Future<?> future = exec.submit(() -> { System.err.println(3 / 0); }); try { Object o = future.get(); } catch (ExecutionException e) { System.err.println("捕獲異常：" + e.getMessage()); } exec.shutdown(); } ``` 【知識點】 1. 如果設置了實例屬性uncaughtExceptionHandler（每個線程對象獨有），則調用該處理器對未捕獲異常進行處理； 2. 如果沒有設置未捕獲異常處理器（即1中的uncaughtExceptionHandler），則將線程對象的ThreadGroup當作未捕獲異常處理器，在ThreadGroup中獲取所以線程對象共享的靜態屬性defaultUncaughtExceptionHandler來處理未捕獲異常（前提是靜態的set方法你調用了并且傳入處理器實例\)； 3. 如果兩個set方法都沒有調用，那么異常棧信息將被推送到System.err進行處理； 【參考資料】 https://blog.csdn.net/reliveIT/article/details/51167545