Any stream with an internal buffer should override this method and provide a much more efficient version that reads the buffer directly, avoiding the extra array allocation on every call.

• 所有具有内部缓冲区的流都应重写此方法,并提供一个可以直接读取缓冲区的更为有效的版本,从而避免每次调用都要进行额外的数组分配。