How to use Java exception handling UncaughtExceptionHandler-javaTutorial-php.cn

Exception handling

Thread uncaught exception UncaughtException requires UncaughtZExceptionHandler for processing

So why do you have to use UncaughtZExceptionHandler?

The main thread can easily capture the thread, but the sub-thread cannot
As can be seen from the following code, even if the sub-thread throws an exception, the main thread will not Unaffected

public class ChildException implements Runnable{ public static void main(String[] args) { new Thread(new ChildException()).start(); for (int i = 0; i < 10; i++) { System.out.println(i); } } @Override public void run() { throw new RuntimeException(); } } /* * Exception in thread "Thread-0" java.lang.RuntimeException at com.jx.JavaTest.Thread.Exception.ChildException.run(ChildException.java:14) at java.lang.Thread.run(Thread.java:748) 0 1 2 3 4 5 6 7 8 9 * */

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As can be seen from the code below, even if you want to use catch to capture child thread exceptions, it is useless
try catch is for the main thread, there is no way to catch the exception of the sub-thread

public class CantCatch implements Runnable { public static void main(String[] args) throws InterruptedException { try { new Thread(new CantCatch(), "thread0").start(); Thread.sleep(300); new Thread(new CantCatch(), "thread1").start(); Thread.sleep(300); new Thread(new CantCatch(), "thread2").start(); Thread.sleep(300); new Thread(new CantCatch(), "thread3").start(); Thread.sleep(300); } catch (RuntimeException e) { System.out.println("catch"); } } @Override public void run() { throw new RuntimeException(); } } /* * Exception in thread "thread0" java.lang.RuntimeException at com.jx.JavaTest.Thread.Exception.CantCatch.run(CantCatch.java:22) at java.lang.Thread.run(Thread.java:748) Exception in thread "thread1" java.lang.RuntimeException at com.jx.JavaTest.Thread.Exception.CantCatch.run(CantCatch.java:22) at java.lang.Thread.run(Thread.java:748) Exception in thread "thread2" java.lang.RuntimeException at com.jx.JavaTest.Thread.Exception.CantCatch.run(CantCatch.java:22) at java.lang.Thread.run(Thread.java:748) Exception in thread "thread3" java.lang.RuntimeException at com.jx.JavaTest.Thread.Exception.CantCatch.run(CantCatch.java:22) at java.lang.Thread.run(Thread.java:748) Process finished with exit code 0 * */

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Exceptions can be caught by try catch in the run method, but it is particularly troublesome because it needs to be done manually Try catch in each run method

UncaughtExceptionHandler

Custom UncaughtExceptionHandler

public class MyUncaughtHandler implements Thread.UncaughtExceptionHandler{ private String name; public MyUncaughtHandler(String name) { this.name = name; } @Override public void uncaughtException(Thread t, Throwable e) { Logger logger = Logger.getAnonymousLogger(); logger.log(Level.WARNING, "线程异常" + t.getName(), e); System.out.println(name + "捕获" + t.getName()+ e); } }

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Use a custom class to catch exceptions

public class UseOwnExceptionHandler implements Runnable { public static void main(String[] args) throws InterruptedException { Thread.setDefaultUncaughtExceptionHandler(new MyUncaughtHandler("MyHandler")); // try { new Thread(new UseOwnExceptionHandler(), "thread0").start(); Thread.sleep(300); new Thread(new UseOwnExceptionHandler(), "thread1").start(); Thread.sleep(300); new Thread(new UseOwnExceptionHandler(), "thread2").start(); Thread.sleep(300); new Thread(new UseOwnExceptionHandler(), "thread3").start(); Thread.sleep(300); // } catch (RuntimeException e) { // System.out.println("catch"); // } } @Override public void run() { // try { throw new RuntimeException(); // } catch (RuntimeException e) { // System.out.println("e"); // } } } /* * 一月 29, 2023 11:22:01 上午 com.jx.JavaTest.Thread.Exception.MyUncaughtHandler uncaughtException 警告: 线程异常thread0 java.lang.RuntimeException at com.jx.JavaTest.Thread.Exception.UseOwnExceptionHandler.run(UseOwnExceptionHandler.java:24) at java.lang.Thread.run(Thread.java:748) MyHandler捕获thread0java.lang.RuntimeException 一月 29, 2023 11:22:01 上午 com.jx.JavaTest.Thread.Exception.MyUncaughtHandler uncaughtException 警告: 线程异常thread1 java.lang.RuntimeException at com.jx.JavaTest.Thread.Exception.UseOwnExceptionHandler.run(UseOwnExceptionHandler.java:24) at java.lang.Thread.run(Thread.java:748) MyHandler捕获thread1java.lang.RuntimeException 一月 29, 2023 11:22:02 上午 com.jx.JavaTest.Thread.Exception.MyUncaughtHandler uncaughtException 警告: 线程异常thread2 java.lang.RuntimeException at com.jx.JavaTest.Thread.Exception.UseOwnExceptionHandler.run(UseOwnExceptionHandler.java:24) at java.lang.Thread.run(Thread.java:748) MyHandler捕获thread2java.lang.RuntimeException 一月 29, 2023 11:22:02 上午 com.jx.JavaTest.Thread.Exception.MyUncaughtHandler uncaughtException 警告: 线程异常thread3 java.lang.RuntimeException at com.jx.JavaTest.Thread.Exception.UseOwnExceptionHandler.run(UseOwnExceptionHandler.java:24) at java.lang.Thread.run(Thread.java:748) MyHandler捕获thread3java.lang.RuntimeException Process finished with exit code 0 * */

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