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.
- 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.
- Instances of the File class are immutable; that is, once created, the abstract pathname represented by a File object will never change.
- 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.
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/javaprogramer");
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
| Field | Type | Description |
|---|---|---|
| pathSeperator | String | the character or string used to separate individual paths in a list of file system paths |
| pathSeperatorChar | 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. |
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
| S. No. | Method | Description | Return Type |
|---|---|---|---|
| 1. | canExecute() | Tests whether the application can execute the file denoted by this abstract pathname. | boolean |
| 2. | canRead() | Tests whether the application can read the file denoted by this abstract pathname. | boolean |
| 3. | canWrite() | Tests whether the application can modify the file denoted by this abstract pathname. | boolean |
| 4. | compareTo(File pathname) | Compares two abstract pathnames lexicographically. | int |
| 5. | createNewFile() | T Atomically creates a new, empty file named by this abstract pathname | boolean |
| 6. | createTempFile(String prefix, String suffix) | Creates an empty file in the default temporary-file directory. | File |
| 7. | delete() | Deletes the file or directory denoted by this abstract pathname. | boolean |
| 8. | equals(Object obj) | Tests this abstract pathname for equality with the given object. | boolean |
| 9. | exists() | Tests whether the file or directory denoted by this abstract pathname exists.. | boolean |
| 10. | getAbsolutePath() | Returns the absolute pathname string of this abstract pathname. | String |
| 11. | list() | Returns an array of strings naming the files and directories in the directory. | String[] |
| 12. | getFreeSpace() | Returns the number of unallocated bytes in the partition. | long |
| 13. | getName() | Returns the name of the file or directory denoted by this abstract pathname. | String |
| 14. | getParent() | Returns the pathname string of this abstract pathname’s parent. | String |
| 15. | getParentFile() | Returns the abstract pathname of this abstract pathname’s parent. | File |
| 16. | getPath() | Converts this abstract pathname into a pathname string. | String |
| 17. | setReadOnly() | Marks the file or directory named so that only read operations are allowed. | boolean |
| 18. | isDirectory() | Tests whether the file denoted by this pathname is a directory. | boolean |
| 19. | isFile() | Tests whether the file denoted by this abstract pathname is a normal file. | boolean |
| 20. | isHidden() | Tests whether the file named by this abstract pathname is a hidden file. | boolean |
| 21. | length() | Returns the length of the file denoted by this abstract pathname. | long |
| 22. | listFiles() | Returns an array of abstract pathnames denoting the files in the directory. | File[] |
| 23. | mkdir() | Creates the directory named by this abstract pathname. | boolean |
| 24. | renameTo(File dest) | Renames the file denoted by this abstract pathname. | boolean |
| 25. | setExecutable(boolean executable) | A convenience method to set the owner’s execute permission. | boolean |
| 26. | setReadable(boolean readable) | A convenience method to set the owner’s read permission. | boolean |
| 27. | setReadable(boolean readable, boolean ownerOnly) | Sets the owner’s or everybody’s read permission.. | boolean |
| 28. | setWritable(boolean writable) | A convenience method to set the owner’s write permission. | boolean |
| 29. | toString() | Returns the pathname string of this abstract pathname. | String |
| 30. | toURI() | Constructs a file URI that represents this abstract pathname. | URI |
File handling is a fundamental aspect of programming, and mastering it is essential for a wide range of applications, from reading configuration files to processing large datasets and managing file-based databases.
Java File Class Examples
Example 1:Program to check if a file or directory physically exists or not.
// In this Java program, we accepts a file or
directory name
// from command line arguments. Then the program
will check
// if that file or directory physically exist
or not and it
// displays the property of that file or directory.
import java.io.File;
// Displaying file property
class fileProperty {
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());
}
}
}
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.
// Java Program to display all
// the contents of a directory
import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;
// Displaying the contents of a directory
class Contents {
public static void main(String[] args)
throws IOException
{
// enter the path and dirname from keyboard
BufferedReader br = new BufferedReader
(new InputStreamReader
(System.in));
System.out.println("Enter dirpath:");
String dirpath = br.readLine();
System.out.println("Enter the dirname");
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.println(arr[i]);
// create File object with the entry and
// test if it is a file or directory
File f1 = new File(arr[i]);
if (f1.isFile())
System.out.println(": is a file");
if (f1.isDirectory())
System.out.println
(": is a directory");
}
System.out.println(
"No of entries in this directory " + n);
}
else
System.out.println("Directory not found");
}
}
