Java.io.File Class in Java

Java File class is Java’s representation of a file or directory pathname. Because file and directory names have different formats on different platforms, a simple string is not adequate to name them. Java File class contains several methods for working with the pathname, deleting and renaming files, creating new directories, listing the contents of a directory, and determining several common attributes of files and directories. 

• It is an abstract representation of files and directory pathnames.
• A pathname, whether abstract or in string form can be either absolute or relative. The parent of an abstract pathname may be obtained by invoking the getParent() method of this class.
• First of all, we should create the File class object by passing the filename or directory name to it. A file system may implement restrictions to certain operations on the actual file-system object, such as reading, writing, and executing. These restrictions are collectively known as access permissions.
• Instances of the File class are immutable; that is, once created, the abstract pathname represented by a File object will never 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. For example, 

File a = new File("/usr/local/bin/geeks");

This defines an abstract file name for the geeks file in the directory /usr/local/bin. This is an absolute abstract file name.

Fields in File Class in Java

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.

Methods of File Class in Java

Java File Class Examples

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

Output

File name :file.txt
Path: file.txt
Absolute path:C:\Users\akki\IdeaProjects\codewriting\src\file.txt
Parent:null
Exists :true
Is writable:true
Is readabletrue
Is a directory:false
File Size in bytes 20

Example 2: Program to display all the contents of a directory

Here we will accept a directory name from the keyboard and then display all the contents of the directory. For this purpose, list() method can be used as: 

String arr[]=f.list();

In the preceding statement, the list() method causes all the directory entries copied into the array arr[]. Then pass these array elements arr[i] to the File object and test them to know if they represent a file or directory.

Output

Enter dirpath:
C:\Users\akki\IdeaProjects\
Enter the dirname
codewriting
.idea
: is a directory
an1.txt
: is a file
codewriting.iml
: is a file
file.txt
: is a file
out
: is a directory
src
: is a directory
text
: is a file
No of entries in this directory 7

Related Post: FileReader and FileWriter in Java

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