How to use File class in java

Author：Eve Cole Update Time：2024-11-18 19:06:02

Constructor

Copy the code code as follows:

public class FileDemo {
public static void main(String[] args){
//Constructor File(String pathname)
File f1 =new File("c://abc//1.txt");
//File(String parent,String child)
File f2 =new File("c://abc","2.txt");
//File(File parent,String child)
File f3 =new File("c:"+File.separator+"abc");//separator cross-platform separator
File f4 =new File(f3,"3.txt");
System.out.println(f1);//c:/abc/1.txt

}

Create method

1.boolean createNewFile() returns true if it does not exist and false if it exists.
2.boolean mkdir() creates a directory
3.boolean mkdirs() creates multi-level directories

Delete method

1.boolean delete()
2.boolean deleteOnExit() delete the file after completion of use

Copy the code code as follows:

import java.io.File;
import java.io.IOException;

public class FileDemo2 {
public static void main(String[] args){
File f =new File("d://1.txt");
try {
System.out.println(f.createNewFile());//Return false when the file exists
System.out.println(f.delete());//Return false when the file does not exist
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

Judgment method

1.boolean canExecute() determines whether the file is executable
2.boolean canRead() determines whether the file is readable
3.boolean canWrite() determines whether the file can be written
4.boolean exists() determines whether the file exists
5.boolean isDirectory()
6.boolean isFile()
7.boolean isHidden()
8.boolean isAbsolute() can also determine whether the absolute path file does not exist.

Get method

1.String getName()
2.String getPath()
3.String getAbsolutePath()
4.String getParent()//If there is no parent directory, return null
5.long lastModified()//Get the time of the last modification
6.long length()
7.boolean renameTo(File f)
8.File[] liseRoots()//Get the machine drive letter
9.String[] list()
10.String[] list(FilenameFilter filter)
List files and folders on disk

Copy the code code as follows:

public class FileDemo3 {
public static void main(String[] args){
File[] files =File.listRoots();
for(File file:files){
System.out.println(file);
if(file.length()>0){
String[] filenames =file.list();
for(String filename:filenames){
System.out.println(filename);
}
}
}
}

}

File filtering

Copy the code code as follows:

import java.io.File;
import java.io.FilenameFilter;
public class FileDemo4 {
public static void main(String[] args){
File[] files =File.listRoots();
for(File file:files){
System.out.println(file);
if(file.length()>0){
String[] filenames =file.list(new FilenameFilter(){
//file filter directory name file name
public boolean accept(File file,String filename){
return filename.endsWith(".mp3");
}
});
for(String filename:filenames){
System.out.println(filename);
}
}
}
}

}

File[] listFiles()

File[] listFiles(FilenameFilter filter)

Use recursion to list all files

Copy the code code as follows:

public class FileDemo5 {
public static void main(String[] args){
File f =new File("e://音");
showDir(f);
}
public static void showDir(File dir){
System.out.println(dir);
File[] files =dir.listFiles();
for(File file:files){
if(file.isDirectory())
showDir(file);
else
System.out.println(file);
}
}

}

Move files

Find all the .java files in the d drive, copy them to the c:/jad directory, and change the types of all files from .java to .jad.

Copy the code code as follows:

public class Test5 {
public static void main(String[] args){
File f1 = new File("d://");
moveFile(f1);
}

public static void moveFile(File dir){
File[] files=dir.listFiles();
for(File file:files){
if(file.isDirectory())
moveFile(file);
else{
if(file.getName().endsWith(".java"))
file.renameTo(new File("c://jad//"+
file.getName().substring(0,file.getName().lastIndexOf('.'))+".jad"));
}
}
}
}