说明：  写一个程序，实现任意类型文件的复制。从命令行输入原始文件名，输出文件与原始文件同名但扩展名为.bak。程序文件命名为Exe6_1.java。
(Write a program that, for any type of file replication. From the command line input to the original file name, output file with the original file name and extension of.Bak. Program file named Exe6_1.java. )