INTRODUCTION ABOUT FILE CLASS IN JAVA

This class is used to represent files and directory paths (but not data of the file, file data is represented by FileInputStream and FileOutputStream). Basically, this class is used to create, delete, rename files and also used to know about the files and directories like, given file name represents file or directory, type of the file is read-only or writable, last modified etc.

Instances of the file class are immutable that is once created, the abstract pathname represented by a file object will never change, because we do not have setter method to change the file name in this file object. But we have getter method to get file name.

Constructors of File class

1. File f = new File(String s) – Creates a java file object to represent name of the file or directory.

2. File f = new File(String subdir, String name) – To create a java file object to represent name of the file or directory, in specified subdirectory.

Methods of File class

1. boolean exists() – Returns true if the specified file or directory is available.

2. boolean createNewFile() – This method first checks whether the physical file is already available or not. If it is already available then this method returns false without creating new file. If it isn’t available then this method creates a new file and returns true.

3. boolean mkdir() – Creates new sub directory with given file name.

4. boolean isFile() – Return true if the underlying file object represents a physical file.

5. boolean isDirectory() – This method checks if subdirectory is available, if so it returns true otherwise false.

6. String[] list() – To list out the names of all files and subdirectories present in the specified directory.

7. long length() – Returns the number of characters present in the file.

8. boolean delete() – To delete the specified file or directory.

Example –

import java.io.File;

import java.io.IOException;

public class File1 {

          public static void main(String[] args) throws IOException {

                   File f = new File("abc.txt");

                   File f1 = new File("xyz");

                   int count=0;

                   boolean a = f.exists();          // already exists so true

                   System.out.println(a);

                   boolean b = f.createNewFile();    // cannot create so false

                   System.out.println(b);

                   boolean c = f1.mkdir();       // created directory xyz inside Project folder

                   System.out.println(c);

                   boolean d = f1.isDirectory();

                   System.out.println(d);          // directory available so true

                   String [] e = f1.list();    // total files in a directory

                   for(String g : e){

                             count++;

                             System.out.println(g);

                   }

                   System.out.println("The total number of files are = "+count);

                   boolean h = f1.delete(); // deleted xyz directory

                   System.out.println(h);

          }

}

Output –

true

false

false

true

The total number of files are = 0

true