File Handling

#java #filehandling #programming

In Java, file handling means working with files like creating them, reading data, writing data or deleting them. It helps a program save and use information permanently on the computer.
Java provides several methods for file handling like creating, reading, updating and deleting the files.

In Java, the File class is used to reprsent the path of a file or a directory in file system. This class is used for creation of files and directories, file searching, file deletion, etc. We need to import java.io.package before using the File class.

How to Create a file Object

To work with a file in Java, you first create a File object by passing the file name or path as a string. The File object represents the actual file/directory on the disk.

import java.io.File;    // Import the File class
File myObj = new File("filename.txt");    // Specify the filename

Following is the list of constructors to create a File object.

-> File(File parent, String child)

This constructor creates a new File instance from a parent abstract pathname and a child pathname string.

-> File(String pathname)

This constructor creates a new File instance by converting the given pathname string into an abstract pathname.

-> File(String parent, String child)

This constructor creates a new File instance from a parent pathname string and a child pathname string.

-> File(URI uri)

This constructor creates a new File instance by converting the given file: URI into an abstract pathname.

Once you have File object in hand, then there is a list of helper methods which can be used to manipulate the files.

-> getName()

-> getAbsolutePath()

-> canRead()

Tests whether the application can read the file denoted by this abstract pathname. Returns true if and only if the file specified by this abstract pathname exists and can be read by the application; false otherwise.

->canWrite()

Tests whether the application can modify to the file denoted by this abstract pathname. Returns true if and only if the file system actually contains a file denoted by this abstract pathname and the application is allowed to write to the file; false otherwise.

->exists()

Tests whether the file or directory denoted by this abstract pathname exists. Returns true if and only if the file or directory denoted by this abstract pathname exists; false otherwise.

-> isDirectory()

Tests whether the file denoted by this abstract pathname is a directory. Returns true if and only if the file denoted by this abstract pathname exists and is a directory; false otherwise.

->isFile()

Tests whether the file denoted by this abstract pathname is a normal file. A file is normal if it is not a directory and, in addition, satisfies other system-dependent criteria. Any non-directory file created by a Java application is guaranteed to be a normal file. Returns true if and only if the file denoted by this abstract pathname exists and is a normal file; false otherwise.

-> length()

-> createNewFile()

Atomically creates a new, empty file. Returns true if the named file does not exist and was successfully created; false if the named file already exists.

-> delete()

Deletes the file or directory denoted by this abstract pathname. If this pathname denotes a directory, then the directory must be empty in order to be deleted. Returns true if and only if the file or directory is successfully deleted; false otherwise.

-> list()