通过File类创建文件失败,该如何处理

public static void main(String[] args) throws IOException {        File dir = new File("c/exam/haha");        if (dir.exists() && dir.isDirectory()) {            System.out.println("The directory already exits!".toUpperCase());        } else {            if (dir.mkdirs()) {                System.out.println("the directory has been created!".toUpperCase());                File f = new File(dir, "test.txt");                f.createNewFile();                f.setReadOnly();                System.out.println("end of creation".toUpperCase());            } else {                System.out.println("failed!".toUpperCase());            }        }    }