Thread.enumerate方法

  Thread.enumerate方法的作用是将当前线程所对应的的线程组包含的所有线程放入一个数组

参见源码注释

/*** Copies into the specified array every active thread in the current* thread's thread group and its subgroups. This method simply* invokes the {@link java.lang.ThreadGroup#enumerate(Thread[])}* method of the current thread's thread group.** <p> An application might use the {@linkplain #activeCount activeCount}* method to get an estimate of how big the array should be, however* <i>if the array is too short to hold all the threads, the extra threads* are silently ignored.</i>  If it is critical to obtain every active* thread in the current thread's thread group and its subgroups, the* invoker should verify that the returned int value is strictly less* than the length of {@code tarray}.** <p> Due to the inherent race condition in this method, it is recommended