scheduleAtFixedRate方法执行问题

Question

刚开始学线程池的定时任务，用到了scheduleAtFixedRate方法，

 package test;

public class work implements Runnable {
    @Override
    public void run() {
        int i=0;
        while(i<10) {
            System.out.println(i++);
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

 package test;

import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

public class errpool {

    public static void main(String[] args) {
        ScheduledExecutorService pool = new ScheduledThreadPoolExecutor(10);
        pool.scheduleAtFixedRate(new work(), 0, 5, TimeUnit.SECONDS);
    }
}

我查的教程说：
当执行任务的时间大于周期间隔时，会发生什么呢？
（1）schedule方法：下一次执行时间相对于 上一次 实际执行完成的时间点 ，因此执行时间会不断延后
（2）scheduleAtFixedRate方法：下一次执行时间相对于上一次开始的 时间点 ，因此执行时间不会延后，存在并发性
按他说的我的定时设置的5秒，但是程序执行要10秒，应该符合第二条，但是实际的运行结果如下

 0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8

并没有出现并发现象，这是为啥呢，求大神解答

Answer 1

看 API
/**
* Creates and executes a periodic action that becomes enabled first
* after the given initial delay, and subsequently with the given
* period; that is executions will commence after
* {@code initialDelay} then {@code initialDelay+period}, then
* {@code initialDelay + 2 * period}, and so on.
* If any execution of the task
* encounters an exception, subsequent executions are suppressed.
* Otherwise, the task will only terminate via cancellation or
* termination of the executor. If any execution of this task
* takes longer than its period, then subsequent executions
* may start late, but will not concurrently execute.
*
* @param command the task to execute
* @param initialDelay the time to delay first execution
* @param period the period between successive executions
* @param unit the time unit of the initialDelay and period parameters
* @return a ScheduledFuture representing pending completion of
* the task, and whose {@code get()} method will throw an
* exception upon cancellation
* @throws RejectedExecutionException if the task cannot be
* scheduled for execution
* @throws NullPointerException if command is null
* @throws IllegalArgumentException if period less than or equal to zero
*/
public ScheduledFuture<?> scheduleAtFixedRate(Runnable command,
long initialDelay,
long period,
TimeUnit unit);

重点在这里：
If any execution of this task takes longer than its period, then subsequent executions may start late, but will not concurrently execute.
如果执行时间比中间的周期长，随后的执行任务可能会晚一点，不会同时执行。
一切 按照API分析