编写一个java应用程序，将一个包含多个子目录和文件的目录复制到另外一个指定的目录下。

1）欲复制的目录中包含的文件数和子目录层次未知，必须在程序执行时获得这些信息。

2）显示欲复制的目录的相关信息。-Write a java application that will contain a number of subdirectories and files copied to another specified directory. 1) To copy the directory containing the files and subdirectories in the number of unknown level, the program must be executed to obtain such information. 2) shows the directory you want to copy the relevant information.