老师说的newSingleThreadExecutor()单线程池在线程异常结束时，会有另一个线程取代，而且源码注释中确实有（if this single thread terminates due to a failure during execution prior to shutdown, a new one will take its place if needed to execute subsequent tasks），但是newFixedThreadPool()也有相同意思的注释（If any thread terminates due to a failure during execution prior to shutdown, a new one will take its place if needed to execute subsequent tasks.），看源码中newSingleThreadExecutor()和newFixedThreadPool()的区别，仅仅是newSingleThreadExecutor()返回的线程池少暴露了一些方法并且多了个finalize方法保证线程池调用shutdown()，所以没看明白这个是怎么实现的。后面用代码测试了一下

public static void main(String[] args) {
        ExecutorService singleThreadExecutor = Executors.newSingleThreadExecutor();
        //Thread.setDefaultUncaughtExceptionHandler(new ThreadExceptionHandler("线程异常捕获器", singleThreadExecutor));

        singleThreadExecutor.execute(new Runnable() {
            private Integer index = 0;
            @Override
            public void run() {
                while (true) {
                    index++;
                    try {
                        TimeUnit.SECONDS.sleep(1);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    if (index == 2) {
                        throw new IllegalStateException("handler exception");
                    }
                    System.out.println(Thread.currentThread().getName() + "NO." + index);
                }
            }
        });
    }

第一次测试我只是在运行中抛出一个异常，由于run()方法不能再抛出异常，线程异常中止，但是并没有另一个线程去取代异常终止的线程去完成剩下的任务。

// 异常捕获
@Override
    public void uncaughtException(Thread thread, Throwable throwable) {
        System.out.println(thread.getName() + " thread aborted abnormally .");
        System.out.println(name + "catch exception ：" +  thread.getName() + "exception：" + throwable);
        singleThreadExecutor.execute(new testThread(0));
    }

之后我加上了异常捕获器，并且在捕获异常后，再一次用之前的线程池去启动线程，达到目的了

执行结果
pool-1-thread-1NO.1
pool-1-thread-1 thread aborted abnormally .
线程异常捕获器catch exception ：pool-1-thread-1exception：java.lang.IllegalStateException: handler exception
pool-1-thread-2NO.1
pool-1-thread-2 thread aborted abnormally .
线程异常捕获器catch exception ：pool-1-thread-2exception：java.lang.IllegalStateException: handler exception
pool-1-thread-3NO.1
pool-1-thread-3 thread aborted abnormally .
线程异常捕获器catch exception ：pool-1-thread-3exception：java.lang.IllegalStateException: handler exception
pool-1-thread-4NO.1
pool-1-thread-4 thread aborted abnormally .
线程异常捕获器catch exception ：pool-1-thread-4exception：java.lang.IllegalStateException: handler exception

所以想问一下老师，singleThreadExecutor是不是需要结合异常捕获的机制，去实现 ” 在线程异常结束时，有另一个线程取代 “ 。