Is it possible to modify a text file whithout copying it in a new one?

Question

Hi all,
In fact I'm trying to use a kind of ini file to configure an application. So I have first to get information in a file using the name of the file, the name of the section and the keyname of the value I want to get. For this no problem. But I just can't change the value. I've read a lot of threads, but whithout finding a solution.
Here is an example of the ini file:
[SECTION1]
KEYWORD1=VALUE1
KEYWORD2=VALUE2
[SECTIONk]
KEYWORD1=VALUE1
KEYWORD2=VALUE2
[SECTIONn]
KEYWORD1=VALUE1
KEYWORD2=VALUE2
And here what I want to have next
[SECTION1]
KEYWORD1=VALUE1
KEYWORD2=VALUE2
[SECTIONk]
KEYWORD1=VALUE1
KEYWORD2=ANOTHERVALUE
[SECTIONn]
KEYWORD1=VALUE1
KEYWORD2=VALUE2
I read the file like this:
buffer = new BufferedReader (new FileReader(sourceFile));
Then I can modify buffer like this:
-I read a line (with buffer.readLine()) to obtain a string called oldString
-I convert it into a StringBuffer
-Next I use the replace method of StringBuffer class
-I can next have a String, I'll call it modifiedString
Now how can I place modifiedString in sourceFile at oldString's place. The only way I found to do this is to create a new file and to copy line after line all the lines from sourceFile, then to delete sourceFile and next to rename the new file in sourceFile. But I think that it's not really good and I'm sure that one (or more) of you has (have) already solve this problem with a better solution.
Thanks a lot.
     S�bastien

Answer 1

The class below remove some words from a file. I suppose you can change it so that it modify a word instead.
import java.io.*;
import java.util.*;
class RemoveWord
     public static void main(String [] arg)
          Vector word=new Vector();
          for(int i=1;i<arg.length;i++)
               word.add(arg);
          removeWord(arg[0],word);
     /*This function removes all the words beeing in the vector "word" from the file fileName     fichier fileName
     public static void removeWord(String fileName,Vector word)
          RandomAccessFile rf =null;
          try
               rf = new RandomAccessFile(fileName, "rw");
               int pos=-1;
               long posCurseur=rf.getFilePointer();
               String ligne=rf.readLine();
               while(ligne!=null)
                    for(int i=0;i<word.size();i++)
                         String wordToRemove=(String)word.get(i);
                         pos=ligne.indexOf(wordToRemove);
                         if(pos!=-1)
                              ligne=ligne.substring(0,pos)+ligne.substring(pos+wordToRemove.length(),ligne.length());
                              for(int j=0;j<wordToRemove.length();j++)
                                   ligne=ligne+" ";     
                              rf.seek(posCurseur);
                              rf.writeBytes(ligne);
                    posCurseur=rf.getFilePointer();
                    ligne = rf.readLine();
          catch(EOFException e){e.printStackTrace();}
          catch(FileNotFoundException e){e.printStackTrace();}
          catch(IOException e){e.printStackTrace();}
          catch(Exception e){e.printStackTrace();}
          finally
               try
                    rf.close();
               catch(IOException e){e.printStackTrace();}