java线程池异常的处理方法

线程池的任务中，会出现一种特殊的异常。在结果上没有输出，但是程序不会抛出报错，这就需要我们对这种异常进行处理。我们先从通过一个实例来分析这种异常的情况，然后为大家带来处理线程池异常的两种方法及代码实例部分。接下来我们看看线程池发生异常的原理和解决办法吧。

1.异常情况

       ExecutorService threadPool = Executors.newFixedThreadPool(5);
        for (int i = 0; i < 5; i++) {
            threadPool.submit(() -> {
                System.out.println("current thread name" + Thread.currentThread().getName());
                Object object = null;
                System.out.print("result## "+object.toString());
            });
        }

虽然没有结果输出，但是没有抛出异常，所以我们无法感知任务出现了异常。

2.异常处理方法

（1）在run方法上增加异常处理

public class FutureTask<V> implements RunnableFuture<V> {
 
    ...
 
    public void run() {
        if (state != NEW ||
            !UNSAFE.compareAndSwapObject(this, runnerOffset,
                                         null, Thread.currentThread()))
            return;
        try {
            Callable<V> 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);
        }
    }
 
    public V get() throws InterruptedException, ExecutionException {
        int s = state;
        if (s <= COMPLETING)
            s = awaitDone(false, 0L);
        return report(s);
    }
 
    private V report(int s) throws ExecutionException {
        Object x = outcome;
        if (s == NORMAL)
            return (V)x;
        if (s >= CANCELLED)
            throw new CancellationException();
        throw new ExecutionException((Throwable)x);
    }
 
}

（2）使用UncaughtExceptionHandler处理未捕获异常

Thread thread = new Thread(() -> {
System.err.println(3 / 2);
System.err.println(3 / 0);
});
thread.setUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() {
@Override
public void uncaughtException(Thread t, Throwable e) {
System.err.println(Thread.currentThread().getName() + "==>" + e.getMessage());
}
});
thread.start();

以上就是java线程池异常的处理方法，在理解了发生这种异常的原理后，我们进一步针对这种情况提出两种解决方法，学会后赶紧尝试着去解决吧。