I/O stream--file class and usage

Introduction to I/O framework

I/O is the interface for computer input/output. Java Core Library Java.io provides a full range of I/O interfaces, including: File system operation, file reading and writing, standard equipment output and so on.

File class and use

① an object of a file class that represents a file or directory on disk.

The ②file class provides a platform-independent way to manipulate files or directories on disk.

The ③file class handles files and file systems directly. For example, delete files, get file length size information.

The ④file class does not provide a way to read from a file or store information in a file.

⑤ Construction Method:

A) File (String directorypath)

b) File (String directorypath,string filename)

c) file (file dirobj,string filename)

⑥file defines a method for getting the standard properties of a file object.

⑦ part of the file class common methods:

A) public String getName ()

b) Public String getParent ()

c) Public File getparentfile ()

d) public String GetAbsolutePath ()

E) public Boolean exists ()

f) Public file[] ListFile ()

g) Public boolean isdirectory ()

h) Public boolean isfile ()

i) public long length ()

j) Boolean Delete ()

K) Boolean mkdir ()

First create a folder named Doc under the D drive and create a txt text file within the folder

1File File =NewFile ("D:\\doc");//Use under \ \ or/,linux under Windows2System.out.println (File.getabsolutepath ());//returns the absolute pathname string for this abstract path name3System.out.println (File.getparent ());//gets the string for the previous level of the directory4System.out.println (File.isdirectory ());//determines whether the file represented by the path name is a directory5System.out.println (File.isfile ());//determines whether the file represented by the pathname is a standard file6System.out.println (File.exists ());//determines whether the file or directory represented by an abstract pathname exists7System.out.println (File.length ());//returns the length of the file represented by this abstract path name8System.out.println (File.delete ());//Delete the file or directory represented by this abstract path name--cannot be deleted if a file exists under the directory

Output results

D:\doc
D:\
True
False
True
0
False

Create directories and directories to create files

1File MyFile =NewFile ("D:\\zhangsan");2System.out.println (Myfile.mkdir ());//Create a directory that does not exist3 4File MyFile2 =NewFile ("D:\\zhangsan\\ceshi.txt");5         Try {6System.out.println (Myfile2.createnewfile ());//Create a file that does not exist under the specified directory7}Catch(IOException e) {8 e.printstacktrace ();9}

Output results

True
True

Enter some characters at random in the Ceshi.txt in the Zhangsan directory and add a picture

Get all the files in the directory

1         string[] files = myfile.list (); // get all the files in the directory 2          for (String f:files) {3            System.out.println (f); 4         }

Output results

Ceshi.txt
Tu.png

Returns all files with the txt suffix

1string[] Files2 = Myfile.list (NewFilenameFilter () {2 3 @Override4              Public BooleanAccept (File dir, String name) {5                 returnName.endswith (". txt");//returns all files with the txt suffix6             }7         });8          for(String f:files2) {9 System.out.println (f);Ten}

Output results

Ceshi.txt

Get all the files, names and sizes in the directory

1         File[] files3=myfile.listfiles (); 2          for (File f:files3) {3             System.out.println (F.getname () + "--" +f.length ()); 4         }

Output results

ceshi.txt--140
tu.png--73425

Returns all files in the directory with the TXT suffix name and size

Method One

1File[] Files4=myfile.listfiles (NewFilenameFilter () {2             3 @Override4              Public BooleanAccept (File dir, String name) {5                 returnName.endswith (". txt");//returns all files with the txt suffix in the directory6             }7         }); 8          for(File f:files4) {9System.out.println (F.getname () + "--" +f.length ());Ten}

Output results

ceshi.txt--140

Method Two

1File[] Files5=myfile.listfiles (NewFileFilter () {2             3 @Override4              Public BooleanAccept (File pathname) {5                 returnPathname.getname (). EndsWith (". txt");6             }7         }); 8          for(File f:files5) {9System.out.println (F.getname () + "--" +f.length ());Ten}

Output results

ceshi.txt--140

I/O stream--file class and usage