Java File Class

The File class in Java is used to represent the path of a file or folder. It helps in creating, deleting, and checking details of files or directories, but not in reading or writing data. It acts as an abstract representation of file and directory names in the system.

Can retrieve parent directories using the getParent() method.
A File object is created by passing a file or directory name to its constructor.
File systems may impose access permissions (read, write, execute).
File objects are immutable. Once created, their pathname cannot change.

How to Create a File Object

A File object is created by passing in a string that represents the name of a file, a String or another File object.

Syntax

File file = new File("path_to_file");

Example 1: Program to check if a file or directory physically exists or not.

Java

import java.io.File;

// Displaying file property
class CheckFileExist {

    public static void main(String[] args){

        // Accept file name or directory name through
        // command line args
        String fname = args[0];

        // pass the filename or directory name to File
        // object
        File f = new File(fname);

        // apply File class methods on File object
        System.out.println("File name :" + f.getName());
        System.out.println("Path: " + f.getPath());
        System.out.println("Absolute path:"
                           + f.getAbsolutePath());
        System.out.println("Parent:" + f.getParent());
        System.out.println("Exists :" + f.exists());

        if (f.exists()) {
            System.out.println("Is writable:"
                               + f.canWrite());
            System.out.println("Is readable" + f.canRead());
            System.out.println("Is a directory:"
                               + f.isDirectory());
            System.out.println("File Size in bytes "
                               + f.length());
        }
    }
}

Output:

Display All Contents of a Directory

This program displays all files and subdirectories inside a given directory using the list() method.

Java

import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;

class AllDir 
{
    public static void main(String[] args)
        throws IOException
    {
        // Enter the path and dirname
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        System.out.print("Enter directory path : ");
        String dirpath = br.readLine();
      
        System.out.print("Enter the directory name : ");
        String dname = br.readLine();

        // Create File object with dirpath and dname
        File f = new File(dirpath, dname);

        // If directory exists,then
        if (f.exists()) {
            
          	// Get the contents into arr[], now arr[i] represent either a File or Directory
            String arr[] = f.list();

            // Find no. of entries in the directory
            int n = arr.length;

            // Displaying the entries
            for (int i = 0; i < n; i++) {

                System.out.print(arr[i] + " ");

                // Create File object with the entry and test if it is a file or directory
                File f1 = new File(f,arr[i]);

                if (f1.isFile())
                    System.out.println(": is a file");
                if (f1.isDirectory())
                    System.out.println(": is a directory");
            }

            System.out.println("\nNo of entries in this directory : " + n);
        }
        else
            System.out.println("Directory not found");
    }
}

Output:

Constructors of Java File Class

File(File parent, String child): Creates a new File instance from a parent abstract pathname and a child pathname string.
File(String pathname): Creates a new File instance by converting the given pathname string into an abstract pathname.
File(String parent, String child): Creates a new File instance from a parent pathname string and a child pathname string.
File(URI uri): Creates a new File instance by converting the given file: URI into an abstract pathname.

Fields in File Class

Field	Type	Description
pathSeparator	String	the character or string used to separate individual paths in a list of file system paths.
pathSeparatorChar	Char	the character used to separate individual paths in a list of file system paths.
separator	String	default name separator character represented as a string.
separatorChar	Char	default name separator character.

Methodsof File Class in Java

Method	Description	Return Type
canExecute()	Checks if the file is executable	boolean
canRead()	Checks if the file is readable	boolean
canWrite()	Checks if the file is writable	boolean
compareTo(File other)	Lexicographically compares pathnames	int
createNewFile()	Atomically creates a new empty file	boolean
createTempFile(String prefix, String suffix)	Creates a temp file in default temp directory	File
delete()	Deletes this file or directory	boolean
exists()	Checks if the file/directory exists	boolean
equals(Object obj)	Compares pathnames for equality	boolean
getAbsolutePath()	Returns absolute pathname as a string	String
getCanonicalPath()	Returns canonical (distinct) pathname	String
getName()	Returns name of file or directory	String
getParent()	Returns parent pathname string	String
getParentFile()	Returns parent as a File object	File
`getPath()`	Returns the original pathname string	String
getFreeSpace()	Returns unallocated bytes in partition	long
length()	Returns file size in bytes	long
isDirectory()	Checks if it’s a directory	boolean
isFile()	Checks if it’s a normal file	boolean
isHidden()	Checks if file is hidden	boolean
lastModified()	Returns last modification time (ms since epoch)	long
list()	Returns names of all entries in directory	String[]
listFiles()	Returns File objects for entries in directory	File[]
listFiles(FileFilter filter)	Filters entries via FileFilter	File[]
listFiles(FilenameFilter filter)	Filters entries via FilenameFilter	File[]
mkdir()	Creates a directory	boolean
mkdirs()	Creates directory including parent dirs	boolean
renameTo(File dest)	Renames or moves file/directory	boolean
setReadOnly()	Marks file/directory as read-only	boolean
setExecutable(boolean exec)	Sets owner's execute permission	boolean
setReadable(boolean read)	Sets owner's read permission	boolean
setReadable(boolean read, boolean ownerOnly)	Sets read permission for owner or all	boolean
setWritable(boolean write)	Sets owner's write permission	boolean
toURI()	Converts pathname to a URI object	URI
toString()	Returns pathname string	String