Java多线程异常抛出后的表现及捕获

一、多线程抛出异常后并不影响主线程及其他子线程的正常执行

 public static void main(String[] args) {System.out.println("Main Thread start");Thread t1 = new Thread(new Runnable() {@Overridepublic void run() {int i = 0;while(i<7) {System.out.println("Thread1 i: "+(i++));try {Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}if (i == 3) {throw new RuntimeException();}}}});Thread t2 = new Thread(new Runnable() {@Overridepublic void run() {int i = 0;while(i<7) {System.out.println("Thread2 i: "+(i++));try {Thread.sleep(1000);} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}});t2.start();t1.start();try {Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}System.out.println("Main Thread end");}

运行结果

Main Thread start
Thread2 i: 0
Thread1 i: 0
Main Thread end
Thread1 i: 1
Thread2 i: 1
Thread1 i: 2
Thread2 i: 2
Exception in thread "Thread-0" java.lang.RuntimeExceptionat cc.eslink.safecheck.domain.dto.req.ProblemReq$1.run(ProblemReq.java:136)at java.lang.Thread.run(Thread.java:748)
Thread2 i: 3
Thread2 i: 4
Thread2 i: 5
Thread2 i: 6Process finished with exit code 0

二、多线程抛出异常主线程无法捕获

public static void main(String[] args) {System.out.println("Main Thread start");Thread t1 = new Thread(new Runnable() {@Overridepublic void run() {int i = 0;while(i<7) {System.out.println("Thread1 i: "+(i++));try {Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}if (i == 3) {throw new RuntimeException();}}}});Thread t2 = new Thread(new Runnable() {@Overridepublic void run() {// TODO Auto-generated method stubint i = 0;while(i<7) {System.out.println("Thread2 i: "+(i++));try {Thread.sleep(1000);} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}});t2.start();try{t1.start();}catch (RuntimeException e){System.out.println("异常捕获");e.printStackTrace();}try {Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}System.out.println("Main Thread end");}

运行结果

Main Thread start
Thread2 i: 0
Thread1 i: 0
Main Thread end
Thread2 i: 1
Thread1 i: 1
Thread1 i: 2
Thread2 i: 2
Thread2 i: 3
Exception in thread "Thread-0" java.lang.RuntimeExceptionat cc.eslink.safecheck.domain.dto.req.ProblemReq$1.run(ProblemReq.java:136)at java.lang.Thread.run(Thread.java:748)
Thread2 i: 4
Thread2 i: 5
Thread2 i: 6Process finished with exit code 0

三、捕获异常
Thread.UncaughtExceptionHandler是当线程因未捕获的异常而突然终止时调用的处理程序接口。

当一个线程由于未捕获的异常而即将终止时，Java虚拟机将使用它来查询线程的 UncaughtExceptionHandler Thread.getUncaughtExceptionHandler()，并将调用该处理程序的 uncaughtException方法，并将该线程和异常作为参数传递。如果某个线程没有显式设置其UncaughtExceptionHandler，则其ThreadGroup对象将充当其 UncaughtExceptionHandler。如果ThreadGroup对象没有处理异常的特殊要求，它可以将调用转发到默认的未捕获异常处理程序。

public static void main(String[] args) {System.out.println("Main Thread start");Thread t1 = new Thread(new Runnable() {@Overridepublic void run() {int i = 0;while(i<7) {System.out.println("Thread1 i: "+(i++));try {Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}if (i == 3) {throw new RuntimeException();}}}});Thread t2 = new Thread(new Runnable() {@Overridepublic void run() {// TODO Auto-generated method stubint i = 0;while(i<7) {System.out.println("Thread2 i: "+(i++));try {Thread.sleep(1000);} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}});Thread.UncaughtExceptionHandler handler = new Thread.UncaughtExceptionHandler() {public void uncaughtException(Thread th, Throwable ex) {System.out.println("Uncaught exception: " + ex);}};t2.start();t1.setUncaughtExceptionHandler(handler);t1.start();try {Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}System.out.println("Main Thread end");}

运行结果

Main Thread start
Thread2 i: 0
Thread1 i: 0
Main Thread end
Thread1 i: 1
Thread2 i: 1
Thread2 i: 2
Thread1 i: 2
Thread2 i: 3
Uncaught exception: java.lang.RuntimeException
Thread2 i: 4
Thread2 i: 5
Thread2 i: 6Process finished with exit code 0

四线程池中异常捕获

1、execute方法，子线程中有异常会抛出异常；

 public static void main(String[] args) {ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(2, 5, 1000, TimeUnit.SECONDS, new ArrayBlockingQueue<Runnable>(10));
for (int i=0;i<10;i++) {threadPoolExecutor.execute(()->doTask("execute"));}threadPoolExecutor.shutdown();}private static void doTask(String string)throws RuntimeException {String str = "ThreadName:"+ Thread.currentThread().getName()+"执行方式:"+string;System.out.println(str);List list = null;System.out.println(list.size());      }

2、submit方法，子线程中有异常不会抛出，需要使用future.get()方法获取异常信息；

public class ThreadPools {public static void main(String[] args) {ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(2, 5, 1000, TimeUnit.SECONDS, new ArrayBlockingQueue<Runnable>(10));for (int i=0;i<10;i++) {Future future =  threadPoolExecutor.submit(()->doTask("submit"));try {future.get();} catch (InterruptedException e) {e.printStackTrace();} catch (ExecutionException e) {e.printStackTrace();}}threadPoolExecutor.shutdown();}private static void doTask(String string)throws RuntimeException {String str = "ThreadName:"+ Thread.currentThread().getName()+"执行方式:"+string;System.out.println(str);List list = null;System.out.println(list.size());/* try {System.out.println(list.size());}catch (Exception e) {System.out.println(e.getMessage());}
*/}
}

但是如果子线程中异常在子线程中被捕获到没有抛出，future.get()方法不会获取到异常信息；

public class ThreadPools {public static void main(String[] args) {ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(2, 5, 1000, TimeUnit.SECONDS, new ArrayBlockingQueue<Runnable>(10));for (int i=0;i<10;i++) {Future future =  threadPoolExecutor.submit(()->doTask("submit"));try {future.get();} catch (InterruptedException e) {e.printStackTrace();} catch (ExecutionException e) {e.printStackTrace();}}threadPoolExecutor.shutdown();}private static void doTask(String string)throws RuntimeException {String str = "ThreadName:"+ Thread.currentThread().getName()+"执行方式:"+string;System.out.println(str);List list = null;try {System.out.println(list.size());}catch (Exception e) {System.out.println(e.getMessage());}}