How to edit parts of a line in a text file in java

Question

I'm trying to delete the last four characters of all the lines in a text file. Let's say I have domain.txt and the content:

123.com 

student.com

tech.net

running into hundreds of lines. How do I delete the last four characters (the extensions) to remain:

123

student

tech

etc.

Answer 1

I hope this helps.

UPDATED

    String a ="123.com";
    System.out.println(a.substring(0, a.lastIndexOf(".")));

Answer 2

You can do as below :

   File file = new File("file.txt");
   BufferedReader reader = new BufferedReader(new FileReader(file));
   String line = "", 
   newtext = "";
   while((line = reader.readLine()) != null) {
      line=line.substring(0, line.lastIndexOf("."))

      newtext += line + "\n";
  }
  reader.close();

 // Now write new Content

  FileWriter writer = new FileWriter("file.txt");
  writer.write(newtext);
  writer.close();

Do not forget to use try..catch