提前在src 目录下准备test.txt 文件 ，参数为命令行参数为 java xxx.class  src\\test.txt src\\test2.txt src\\test.txt src\\test2.txt

static void copy(String source, String target) throws IOException {

		// 友情提示：测试时请使用无关紧要的文件

		// TODO:

	

		try(    InputStream fin = new FileInputStream(source);

				BufferedInputStream finbuf = new BufferedInputStream(fin);

				OutputStream fout = new FileOutputStream(target);

				BufferedOutputStream foutbuf = new BufferedOutputStream(fout);){

			   

			byte [] cache = new byte[20480];

			int n;

			while((n=finbuf.read(cache,0,20480))!=-1 ) {

				foutbuf.write(cache,0,n);

			}

			

		}

	}