Replace a line or word in a file from java programing

Replace a line or word in a file  when you create a file form java program and need some change by coding like change any word or line created file then do some code as like we providing to you better solution of changing a  line or word from java code that file is created by java code.

import java.io.*;

public class BTest
    {
     public static void main(String args[])
         {
         try
             {
             File file = new File("file.txt");
             BufferedReader reader = new BufferedReader(new FileReader(file));
             String line = "", oldtext = "";
             while((line = reader.readLine()) != null)
                 {
                 oldtext += line + "\r\n";
             }
             reader.close();
             // replace a word in a file
             //String newtext = oldtext.replaceAll("drink", "Love");
            
             //To replace a line in a file
             String newtext = oldtext.replaceAll("This is test string 20000", "blah blah blah");
            
             FileWriter writer = new FileWriter("file.txt");
             writer.write(newtext);writer.close();
         }
         catch (IOException ioe)
             {
             ioe.printStackTrace();
         }
     }
}

file.txt
I drink Java
I sleep Java
This is test string 1
This is test string 20000