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Java Change File-Extension

In this program you will learn how to change the file extension of the file.

Java Change File-Extension


In this program you will learn how to change the file extension of the file. Here you will be asked to enter the file name whose extension is to be changed and then you will get the file name with the changed extension..

Description of the code:

In the program code given below, you will be asked to enter the file name with the extension as can be observed from the method of*; package which is BufferedReader();. The compiler will read the file name as oldfileExtension once you enter it through readLine(); method. Then it will check for that filename if it exists or not. If it will find the mentioned filename then change it by asking you to enter a new fileextension. For this we have used a constructor and we have passed the newfileExtension to that. Then we have applied renameTo(); to change the filename. Remember we haven't changed the filename here but file extension only.

The code of the program is given below:


public class ChangeFileExt{
  public static void main(String[] argsthrows IOException{
  BufferedReader in = new BufferedReader(new InputStreamReader(;
  System.out.print("Please enter the filename with extension to be changed: ");
  String oldfileExtension = in.readLine();
  File oldfile = new File(oldfileExtension);
  System.out.println("File does not exist.");
  int dotPos = oldfileExtension.lastIndexOf(".");
  String strExtension = oldfileExtension.substring(dotPos + 1);
  String strFilename = oldfileExtension.substring(0, dotPos);
  String newfileExtension = in.readLine();
  String strNewFileName = strFilename + "." + newfileExtension;
  File newfile = new File(strNewFileName);
  boolean Rename = oldfile.renameTo(newfile);
  if(!Rename)  {
  System.out.println("FileExtension hasn't been changed successfully.");
  else {
  System.out.println("FileExtension has been changed successfully.");

Output of the program:


C:\java-examples>java ChangeFileExt
Please enter the filename with extension to be changed: amit.txt
Enter file extension to change the file type: java
FileExtension has been changed successfully.


Download this example. 


Posted on: August 18, 2007 If you enjoyed this post then why not add us on Google+? Add us to your Circles

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sara varghese
August 20, 2011
to execute this code

how to execute this code? which software i have to install that?
March 8, 2012
why strExtension ?

Why strExtension is not use ?