Advanced API (use of file class)

File The acquisition function of

Get file size ：file.length()

Get the absolute path of the file ：file.getAbsolutePath()

Get the path of the file ：file.getPath()

Get the name of the file ：file.getName()

Get the last modification time of the file （1970 year 1 month 1 Millisecond value of day ）：file.lastModified()

long time = file.lastModified();
adopt util In bag Date Object to convert
Date date = new Date(time);
System.out.println(date.toLocaleString());
SimpleDateFormat sdf = new SimpleDateFormat("yyyy year MM month dd Japan HH:mm:ss");
System.out.println(sdf.format(date));

File Class

1. Judgment method
         *                 exists   Judge whether it exists
         *                 isFile   Determine whether or not to file
         *                 isHidden Determine whether it is a hidden file
         *                 isDirectory Determine whether it is a folder
         * 
         *             2. New features
         *                 createNewFile   Create a new file   There are abnormal
         *                 mkdir   Create a single folder
         *                 mkdirs   Create multi-level folders
         * 
         *             3. Delete function
         *                 delete   Delete file , Delete folder must be empty
         *     
         *             4. Acquisition function
         *                 length   To obtain the length of the （ byte ）
         *                 getPath   Path to file
         *                 getAbsolutePath   The absolute path to the file
         *                 getName   The name of the document
         *                 lastModified   Last modified time
         *                 listRoots   Disk root
         *                 list   All files and folder names in a directory
         *                 listFiles   All file objects in a directory

                            Construction method  new File(String filePath);

Java Recursive method of  
     demand ： complete 1+2+3....+100 Result   5050 
      @param args
       public static int mySum(int num) {
        if(num == 1) {
            return 1;
        }
        return num+mySum(num-1);//  1+2+3 mySum(1)
    }