打印该目录所有文件名称

public static void listDirectory(File dir) throws IOException{
        if(!dir.exists()) {
            System.out.println("目录：" +dir + "不存在");
            throw new IllegalArgumentException();
        }

        String[] files = dir.list();

        if(files.length > 0 && files != null){
            for (String string : files) {
                if(new File(dir + "\\" + string).isDirectory()) {
                    listDirectory(new File(dir + "\\" + string));
                }else {
                    System.out.println(dir + "\\" + string);
                }
            }
        }