Java Program to Get the File Extension

May 25, 2023

What is File Extension ?

A file extension is the set of characters that appear after the last period (dot) in a file name and determine the type of file it is. The file extension provides information about the format of the file and the type of information it contains, which helps the operating system or software applications determine how to handle the file. For example, a file with the extension .txt is a plain text file, while a file with the extension .jpg is a JPEG image file.

File extensions and their associated file types include:

.txt: plain text file
.doc: Microsoft Word document
.docx: Microsoft Word Open XML document
.xls: Microsoft Excel spreadsheet
.pdf: Portable Document Format file
.jpg: JPEG image file
.png: Portable Network Graphics image file
.mp3: MP3 audio file
.mp4: MP4 video file
.java: Java source code file

Ways to Convert int into double :

1. Using the substring() method :

String fileName = "example.txt";
int indexOfDot = fileName.lastIndexOf(".");
String fileExtension = fileName.substring(indexOfDot + 1);

Explanation :

In this example, we use the lastIndexOf method to find the last occurrence of the dot (.) in the file name. We then use the substring method to extract the characters after the dot, which is the file extension.

2. Using the split method :

String fileName = "example.txt";
String[] parts = fileName.split("\\.");
String fileExtension = parts[parts.length - 1];

Explanation :

In this example, we use the split method to split the file name into an array of strings using the dot (.) as the delimiter. The last element of the array is the file extension.

3. Using the Path class :

import java.nio.file.Path;
import java.nio.file.Paths;

String fileName = "example.txt";
Path path = Paths.get(fileName);
String fileExtension = path.getFileName().toString().split("\\.")[1];

Explanation :

In this example, we use the Paths.get method to create a Path object from the file name. We then use the getFileName method to get the FileName object, which represents the file name without the directory information. We use the toString method to get the string representation of the FileName object, and then split it using the split method to get the file extension.

Note : These are some of the ways to determine the file extension in Java. The appropriate method to use depends on the specific requirements of your program.

Example : Using the substring() method

Run

class Main {
  public static void main(String[] args) {
    String fileName = "example.txt";
    int indexOfDot = fileName.lastIndexOf(".");
    String fileExtension = fileName.substring(indexOfDot + 1);
    System.out.println("File extension using substring method: " + fileExtension);
  }
}

Output :

File extension using substring method: txt

Explanation : In this method, we first find the last occurrence of the dot (.) in the file name using the lastIndexOf method. Then, we use the substring method to extract the characters after the dot, which is the file extension. The substring method takes two arguments: the start index and the end index. In this case, we start from the index after the dot (indexOfDot + 1) and extract all the characters until the end of the string.

Example : Using the split method

Run

class Main {
  public static void main(String[] args) {
    String fileName = "example.txt";
    String[] parts = fileName.split("\\.");
    String fileExtension = parts[parts.length - 1];
    System.out.println("File extension using split method: " + fileExtension);
  }
}

Output :

File extension using split method: txt

Explanation : In this method, we use the split method to split the file name into an array of strings using the dot (.) as the delimiter. The split method takes one argument: the regular expression that represents the delimiter. In this case, we need to escape the dot (.) because it has a special meaning in regular expressions. The last element of the array is the file extension.

Example : Using the Path class

Run

import java.nio.file.Path;
import java.nio.file.Paths;

class Main {
  public static void main(String[] args) {
    String fileName = "example.txt";
    Path path = Paths.get(fileName);
    String fileExtension = path.getFileName().toString().split("\\.")[1];
    System.out.println("File extension using Path class: " + fileExtension);
  }
}

Output :

File extension using Path class: txt

Explanation : In this method, we use the Paths.get method to create a Path object from the file name. The Paths.get method takes one argument: the file name. We then use the getFileName method to get the FileName object, which represents the file name without the directory information. We use the toString method to get the string representation of the FileName object, and then split it using the split method to get the file extension.

Prime Course Trailer

Related Banners

Get PrepInsta Prime & get Access to all 200+ courses offered by PrepInsta in One Subscription

Get over 200+ course One Subscription

Courses like AI/ML, Cloud Computing, Ethical Hacking, C, C++, Java, Python, DSA (All Languages), Competitive Coding (All Languages), TCS, Infosys, Wipro, Amazon, DBMS, SQL and others

Java Program to Get the File Extension

What is File Extension ?

File extensions and their associated file types include:

Ways to Convert int into double :

Explanation :

Explanation :

Explanation :

Example : Using the substring() method

Output :

Example : Using the split method

Output :

Example : Using the Path class

Output :

Prime Course Trailer

Related Banners

Get over 200+ course One Subscription

Checkout list of all the video courses in PrepInsta Prime Subscription

Checkout list of all the video courses in PrepInsta Prime Subscription