ThreadPoolExecutor with corePoolSize 0 should not execute tasks until task queue is full

Question

I was going through Java Concurrency In Practice and got stuck at the 8.3.1 Thread creation and teardown topic. The following footnote warn

Answer 1

Seems like it was a bug with older java versions but it doesn't exist now in Java 1.8.

According to the Java 1.8 documentation from ThreadPoolExecutor.execute():

     /*
     * Proceed in 3 steps:
     *
     * 1. If fewer than corePoolSize threads are running, try to
     * start a new thread with the given command as its first
     * task.  The call to addWorker atomically checks runState and
     * workerCount, and so prevents false alarms that would add
     * threads when it shouldn't, by returning false.
     *
     * 2. If a task can be successfully queued, then we still need
     * to double-check whether we should have added a thread
     * (because existing ones died since last checking) or that
     * the pool shut down since entry into this method. So we
     * recheck state and if necessary roll back the enqueuing if
     * stopped, or start a new thread if there are none.
     * ....
     */

In the second point, there is a recheck after adding a worker to the queue that if instead of queuing the task, a new thread can be started, than rollback the enqueuing and start a new thread.

This is what is happening. During first check the task is queued but during recheck, a new thread is started which executes your task.