Java Io learning notes (1): File class

Source: Internet
Author: User
ArticleDirectory
    • Instance operation 1: Create a new file
    • Instance operation 2: delete a specified file
    • Instance operation 3: Create and delete files comprehensively
    • Instance operation 4: Create a folder
    • Instance operation 5: list all files in the specified directory
    • Instance operation 6: Determine whether a specified path is a directory
    • Instance operation 7: list all contents of a specified directory

In the entire Io package, the only class that indicates the file itself is the file class. You can use the File class to create or delete files. To use the File class. First, observe the construction method of the file class. The common construction methods of this class are as follows:

Public file (string pathname)When instantiating the file class, you must set the path

No.

Method or constant

Type

Description

1

Public static final string pathseparator

Constant

Path separator (";" for Windows)

2

Public static final string Separator

Constant

Path separator ("\" for Windows)

3

Public file (string pathname)

Structure

Create a file object and pass in the complete path

4

Public Boolean createnewfile () throws ioexception

Normal

Create a new file

5

Public Boolean Delete ()

Normal

Delete an object

6

Public Boolean exists ()

Normal

Determine whether a file exists

7

Public Boolean isdirectory ()

Normal

Determines whether the specified path is in a directory.

8

Public long length ()

Normal

Size of the returned File

9

Public String [] list ()

Normal

Lists all the contents of a specified directory, just the name

10

Public file [] listfiles ()

Normal

Lists all the contents of a specified directory, with a path

11

Public Boolean mkdir ()

Normal

Create a directory

12

Public Boolean renameto (File DEST)

Normal

Rename an existing file

 

Instance operation 1: Create a new file

Create a test.txt file on the ddrive

 1   Import Java. Io. file;
2 Import Java. Io. ioexception;
3
4 Public Class Test1 {
5 Public Static Void Main (string [] ARGs ){
6 File F = New File ("D:" + file. Separator + "test.txt "); // To increase portability, we recommend that you use file. separator.
7 Try {
8 F. createnewfile ();
9 } Catch (Ioexception e ){
10 E. printstacktrace ();
11 }
12 }
13 }
Instance operation 2: delete a specified file

Delete the created test.txt File

 1   Import Java. Io. file;
2
3 Public Class Test2 {
4 Public Static Void Main (string [] ARGs ){
5 File F = New File ("D:" + file. Separator + "test.txt ");
6 If (F. exists ()){ // Check whether the file does not exist. If the file does not exist, you do not need to delete it.
7 F. Delete ();
8 }
9 }
10 }

 

Instance operation 3: Create and delete files comprehensively

Given a path. If this file exists, it will be deleted. If it does not exist, it will be created.

 1   Import Java. Io. file;
2 Import Java. Io. ioexception;
3
4 Public Class Test3 {
5 Public Static Void Main (string [] ARGs ){
6 File F = New File ("D:" + file. Separator + "test.txt ");
7 If (F. exists ()){
8 F. Delete ();
9 } Else {
10 Try {
11 F. createnewfile ();
12 } Catch (Ioexception e ){
13 E. printstacktrace ();
14 }
15 }
16 }
17 }

 

Instance operation 4: Create a folder

Create a folder using the mkdir () method

1 ImportJava. Io. file;
2
3 Public ClassTest4 {
4Public Static VoidMain (string [] ARGs ){
5File F =NewFile ("D:" + file. Separator + "test ");
6F. mkdir ();//Create a folder
7}
8}

 

Instance operation 5: list all files in the specified directory

If a directory is provided, the contents in the directory can be listed directly. However, the methods listed include two in the file class:

    • Return in the form of a string array: Public String [] list ()
    • Return in the form of a file array: Public file [] listfiles ()

Operation 1: Use List () to list all content

 1   Import Java. Io. file;
2
3 Public Class Test5 {
4 Public Static Void Main (string [] ARGs ){
5 File F = New File ("D:" + file. separator );
6 String [] STR = f. List ();
7 For (String S: Str ){
8 System. Out. println (s );
9 }
10 }
11 }

All the names are listed above, including the folder name and file name.

Operation 2: Use listfiles () to list

1   Import Java. Io. file;
2
3 Public Class Test6 {
4 Public Static Void Main (string [] ARGs ){
5 File F = New File ("D:" + file. separator );
6 File [] files = f. listfiles ();
7 For (File file: Files ){
8 System. Out. println (File );
9 }
10 }
11 }

The complete path is listed above.

 

Instance operation 6: Determine whether a specified path is a directory

Determine whether the path is a directory

 1   Import Java. Io. file;
2
3 Public Class Test7 {
4 Public Static Void Main (string [] ARGs ){
5 File F = New File ("D:" + file. separator );
6 If (F. isdirectory ()){
7 System. Out. println (F. getpath () + "is a directory ");
8 } Else {
9 System. Out. println (F. getpath () + "not a directory ");
10 }
11 }
12 }

 

Instance operation 7: list all contents of a specified directory

If a directory is specified, all files in this directory must be listed, including files in subfolders.

 1   Import Java. Io. file;
2
3 Public Class Test8 {
4 Public Static Void Main (string [] ARGs ){
5 File F = New File ("D:" + file. separator );
6 Print (f );
7 }
8 Public Static Void Print (file F ){
9 If (F! = Null ){
10 If (F. isdirectory ()){
11 File [] files = f. listfiles ();
12 If (Files! = Null ){
13 For (File file: Files ){
14 Print (File );
15 }
16 }
17 } Else {
18 System. Out. println (f );
19 }
20 }
21 }
22 }

Summary:

    1. The file class is unique in the Java. Io package and is related to the file itself.
    2. Common file operations such as file creation and Deletion
    3. When using the file class to specify the path, be sure to pay attention to the differences between operating systems and try to use separator for segmentation.

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.