java捕获线程异常

在jdk1.5之前，线程不允许抛出异常（各个线程要把自己的checked exception处理掉），但是无法避免的是uncheckedexception，也就是RuntimeException，当抛出异常时子线程会结束，但不会影响主线程。主线程通过try catch是无法捕获子线程异常的，Thread对象提供了setUncaughtExceptionHandler(Thread.UncaughtExceptionHandlereh)方法用来获取线程中产生的异常。

import java.lang.Thread.UncaughtExceptionHandler;

public class ThreadTest1 {

  public static void main(String[] args) {
    MyThread my = new MyThread();
    my.setUncaughtExceptionHandler(new UncaughtExceptionHandler() {
      public void uncaughtException(Thread t, Throwable e) {
        System.out.println(t.getName() + " : " + e.getMessage());
        // TODO
      }
      });
    try {
      my.start();
    } catch (Exception e) {
      System.out.println("error");
    }
  }
  
  public static class  MyThread extends Thread {
    public MyThread() {}
    public void run() {
        System.out.println("abc");  
        throw new RuntimeException("just a test");
  }
  }
}

注：下面这种方式无法捕获到线程中抛出的异常。

public static void main(String[] args) {
  MyThread my = new MyThread();
  try {
    my.start();
  } catch (Exception e) {
    System.out.println("error");
  }
}

在jdk1.5以后，引入了callable，该类可以让线程又返回值，同时可以抛出异常。如下：

public class ThreadTest2 {

  public static void main(String[] args) {
    ExecutorService pool = Executors.newFixedThreadPool(2); 
    Callable<String> c1 = new MyThread();
    Future<String> future = pool.submit(c1);
    
    try {
      System.out.println(future.get());
    } catch (Exception e) {
      System.out.println("error....");
    } finally {
      pool.shutdown();
    }
  }
  
  public static class  MyThread implements Callable<String> {
    public MyThread() {}
  
    @Override
    public String call() throws Exception {
      int a = 1/0;
      return "abc";
    }
  }
}