Executor Service Leak (ARCH4040)

Key java.async.executor-service-leak · Severity warning · Category async

An ExecutorService created via Executors.newFixedThreadPool and never shut down leaks non-daemon threads and can prevent the JVM from exiting.

Incorrect

void run(List<Task> tasks) {
    ExecutorService pool = Executors.newFixedThreadPool(4);
    tasks.forEach(t -> pool.submit(t)); // never shut down
}

Correct

void run(List<Task> tasks) {
    ExecutorService pool = Executors.newFixedThreadPool(4);
    try {
        tasks.forEach(pool::submit);
    } finally {
        pool.shutdown();
    }
}

Fix

Shut the ExecutorService down with shutdown() in a finally block, or use try-with-resources.