public static void main(String[] args) {
        File srcDir = new File("D:\\source");
        File targetDir = new File("D:\\target");
        copyDir(srcDir, targetDir);
    }

    private static void copyDir(File srcDir, File targetDir){
        if (srcDir.isFile()) {
            try {
                FileUtils.copyFile(srcDir, targetDir);
            } catch (IOException e) {
                System.out.println("复制文件出错");
                e.printStackTrace();
            }
        } else {//是一个文件夹
            targetDir.mkdir();
            String[] files = srcDir.list();
            for (String childFile : files) {
                File srcChildFile = new File(srcDir, childFile);
                File targetChildFile = new File(targetDir, childFile);
                copyDir(srcChildFile, targetChildFile);
            }
        }
    }