What causes "runnable nullPointerException" in crossoverJie/JCSprout?

Ensure the Runnable passed to execute()/submit() is never null — assign a no-op or throw a clearer IllegalArgumentException in your own code first.

crossoverJie/JCSprout · error · NullPointerException

runnable nullPointerException

Error message

runnable nullPointerException

What it means

CustomThreadPool.execute() throws a NullPointerException when the submitted Runnable is null, mirroring the contract of java.util.concurrent.ThreadPoolExecutor.execute(). The pool needs a concrete task to schedule onto a worker thread, so a null reference is treated as a programmer error rather than silently ignored.

Source

Thrown at src/main/java/com/crossoverjie/concurrent/CustomThreadPool.java:117

     * @param callable
     * @param <T>
     * @return
     */
    public <T> Future<T> submit(Callable<T> callable) {
        FutureTask<T> future = new FutureTask(callable);
        execute(future);
        return future;
    }


    /**
     * 执行任务
     *
     * @param runnable 需要执行的任务
     */
    public void execute(Runnable runnable) {
        if (runnable == null) {
            throw new NullPointerException("runnable nullPointerException");
        }
        if (isShutDown.get()) {
            LOGGER.info("线程池已经关闭，不能再提交任务！");
            return;
        }

        //提交的线程 计数
        totalTask.incrementAndGet();

        //小于最小线程数时新建线程
        if (workers.size() < miniSize) {
            addWorker(runnable);
            return;
        }


        boolean offer = workQueue.offer(runnable);
        //写入队列失败

View on GitHub (pinned to fc4c6e5f6d)

Solutions

Ensure the Runnable passed to execute()/submit() is never null — assign a no-op or throw a clearer IllegalArgumentException in your own code first.
If the task is optional, guard the call: if (runnable != null) pool.execute(runnable);
When calling submit(), validate the Callable argument before passing it.

Example fix

// before
pool.execute(maybeNullTask);

// after
if (runnable != null) {
    pool.execute(runnable);
} else {
    LOGGER.warn("skipping null task submission");
}

Defensive patterns

Strategy: validation

Validate before calling

Objects.requireNonNull(runnable, "runnable must not be null before submitting to pool");
pool.execute(runnable);

Prevention

Always validate task arguments with Objects.requireNonNull before calling execute() or submit().
Avoid conditional expressions that can yield null (condition ? task : null); use an explicit if-guard instead.
If tasks come from a factory, have the factory return an empty Runnable rather than null.

When it happens

Trigger: Calling execute(null) directly, or submit(callable) where callable is null (submit wraps the callable in a FutureTask and forwards to execute). Also triggered when a method reference or supplier returns null and the result is passed in.

Common situations: Passing a conditional expression that evaluates to null (e.g. condition ? task : null). Submitting a task obtained from a factory or lookup that can return null. Copy-paste where the runnable variable was never assigned.

Related errors

counter < 0

AI-assisted analysis of crossoverJie/JCSprout@fc4c6e5f6d (2026-08-14). Data as JSON: /api/errors/c43716846b4667bc. Report an issue: GitHub.