大家都知道提交任务到线程池有execute和submit两种方式，如果业务处理出异常了，前者会抛出堆栈信息，后者不会，至于为什么，大家可以去看看源码就知道了。
不过我这里有个疑问，就是Doug Lea大神为什么会设计成一种可以抛异常，一种不抛而是自己吞掉呢？
基于这段代码，我是这样想的
final void runWorker(Worker w) {
Thread wt = Thread.currentThread();
Runnable task = w.firstTask;
w.firstTask = null;
w.unlock(); // allow interrupts
boolean completedAbruptly = true;
try {
while (task != null || (task = getTask()) != null) {
w.lock();
// If pool is stopping, ensure thread is interrupted;
// if not, ensure thread is not interrupted. This
// requires a recheck in second case to deal with
// shutdownNow race while clearing interrupt
if ((runStateAtLeast(ctl.get(), STOP) ||
(Thread.interrupted() &&
runStateAtLeast(ctl.get(), STOP))) &&
!wt.isInterrupted())
wt.interrupt();
try {
beforeExecute(wt, task);
Throwable thrown = null;
try {
task.run();
} catch (RuntimeException x) {
thrown = x; throw x;
} catch (Error x) {
thrown = x; throw x;
} catch (Throwable x) {
thrown = x; throw new Error(x);
} finally {
afterExecute(task, thrown);
}
} finally {
task = null;
w.completedTasks++;
w.unlock();
}
}
completedAbruptly = false;
} finally {
processWorkerExit(w, completedAbruptly);
}
}
processWorkerExit(w, completedAbruptly); 这句执行到的前提是：线程池中有线程处理任务出现异常了，为什么？ 因为while (task != null || (task = getTask()) != null) 会一直阻塞嘛，它里面的逻辑就是把这个异常线程从woker中移除掉，好，也就是说必须抛了异常才能跑到这里，而execute方式如果异常了就能走到这里。
而submit提交方式是不会抛出异常的，因为它走的是下面这段代码，setException(ex)这句吞掉了异常， 代码在FutureTask中
public void run() {
if (state != NEW ||
!UNSAFE.compareAndSwapObject(this, runnerOffset,
null, Thread.currentThread()))
return;
try {
Callable c = callable;
if (c != null && state == NEW) {
V result;
boolean ran;
try {
result = c.call();
ran = true;
} catch (Throwable ex) {
result = null;
ran = false;
setException(ex);
}
if (ran)
set(result);
}
} finally {
// runner must be non-null until state is settled to
// prevent concurrent calls to run()
runner = null;
// state must be re-read after nulling runner to prevent
// leaked interrupts
int s = state;
if (s >= INTERRUPTING)
handlePossibleCancellationInterrupt(s);
}
}
自然的也不会走到上面 processWorkerExit(w, completedAbruptly); 也就是这种提交任务方式不会因为异常而从woker中移除线程。
总结：
根据上面的分析，我个人理解为什么这样设计，是因为 submit 即使出现异常也不会从线程池中移除当前线程，而 execute 会移除，就是可以有两种选择，不知道这样理解的对不对，反正思考了就对了，请路过的大佬多指教~
