code: public CronPattern getPattern(int index) {
  		final Lock readLock = lock.readLock();
  		try {
  			readLock.lock();
  			return patterns.get(index);
  		} finally {
  			readLock.unlock();
  		}
  	}
docs: 获得指定位置的{@link CronPattern}
  
  @param index 位置
  @return {@link CronPattern}
  @since 3.1.1