know Java file extension

Files are usually known through their extensions. An extension differentiates the file from another file. It recognizes the file type. To find the extension from its file is a common task.

You can see in the give example, we have created an object of class File and specify a text file as an argument. The method getName() returns the name of the file. Then we have used substring() method to return a new string consists of file extension.

import java.io.*;

public class ExtensionJava {
	public static void main(String[] args) {
		File file = new File("file.txt");
		String fname = file.getName();
		String ext = fname.substring(fname.lastIndexOf('.') + 1, fname.length());
		System.out.println("Extension of file " + fname + " is: " + ext);
	}

}