Java I/O (I) File class

The input/output stream class processes the reading and writing of file content. The file class indicates the storage information of files and folders, such as the file location and size.

Three types of file structure

File (File parent, string child) file (string pathname) file (string parent, string child)

String Path = "D:" + file. separator + "filetest"; file = new file (PATH); system. out. println (File); // constructed file object. The imported file object is used as the root directory file file2 = new file (file, "subfile"); system. out. println (file2); // constructed file object. The passed String object is used as the root directory file file3 = new file (path, "subfile"); system. out. println (file3 );

Common Methods of the file class: getpath () returns the string of the path, which is equivalent to the tostring () method of the file class. getname () returns the file name, excluding the path exists () whether mkdir () exists in the file/directory: create a level 1 subdirectory under the existing path

Mkdirs () can be used to create a multi-layer directory in an existing path. For example, create the D:/ffffff/filetest/sub directory in drive D.

String path2 = "D:" + File.separator + "ffffff" +File.separator + "filetest" + File.separator+ "sub";File file = new File(path);file.mkdirs();

File. mkdir () cannot create a directory with a layer-4 structure such as D:/ffffff/filetest/Sub. file. mkdirs () can
Whether isfile () is a file
Whether isdirectory () is a directory

Length () returns the length measured in bytes.
Createnewfile () create a file
Getparent () returns the string of the parent directory, the file returns its parent directory, the directory returns the parent directory, and the root directory returns NULL

Getparentfile () returns the file object of the parent directory, same

Renameto (File file) can be renamed, you can change the suffix, such as 1.txt to 2.dat

Standard Path Name Of The GetCanonicalPath () File

Getcanonicalfile () file standard path file object

Delete () delete a file, non-directory

List () lists all level 1 folder names and file names under the file object.

Example: Directory D:/filetestwith folder1folder, test.txt,test2.txt

String path = "D:" +File.separator + "filetest";File file = new File(path);for (String s : file.list())System.out.println(s);

Result: folder1test.txttest2.txt

Corresponding to listfiles (), usage

for (File s : file.listFiles())System.out.println(s);

List (filenamefilter filter) returns the array of file names that meet the filtering conditions of the filenamefilter interface. Usage: Write a class to implement the filenamefilter interface, override the accept method, and write the file filtering logic in the accept.

Example: returns a TXT file in the specified directory.

Class extensionfilter implements filenamefilter {public extensionfilter (string ext) {extension = ". "+ ext ;}@ overridepublic Boolean accept (File Dir, string name) {return name. endswith (Extension);} private string extension ;}..... in the main method: For (string S: file. list (New extensionfilter ("TXT") system. out. println (s );