Bonjour,

Pour trouver l'index (position) d'une chaine de caractère dans une autre tu utilise indexOf.
Ca te retourne un entier (position de départ). Si cet entier vaut -1 c'est que ta chaine n'a pas été trouvée, dans le cas contraire elle a été trouvée.
Dans ce cas, ce qui intéresse est de pouvoir insérer juste avant (et juste après), des balises, autrement dit du texte. Pour cela rien de plus simple, voici un exemple complet (en partant juste de la chaine de caractère)

	public static void FindAndUpdate ( String theInputFileName, String theOutputFileName, String theSymbol, String theCommentSymbol, String theExpression ){
		
		int myStartIndex = -1;
		String myTmpStr	 = null;
		String myOutputString	= "";
		boolean found = false;
		
		RandomAccessFile myInputFile = null;
		RandomAccessFile myOutputFile = null;
		String myLine = null;
		
		try{
			// --- Open the file
			myInputFile = new RandomAccessFile(theInputFileName, "r");
			myOutputFile = new RandomAccessFile(theOutputFileName, "rw");
			
			// --- Read line per line
			while (  (myLine = myInputFile.readLine() ) != null ){
				
				// --- Init the index for the new line
				myStartIndex = -1;
				found = false;
				myOutputString = "";
				
				myTmpStr = myLine;
				// --- And for each line, search the pattern 'theSymbol' and try to comment it
				while ( myTmpStr != "" && (myStartIndex = myTmpStr.indexOf(theSymbol)) != -1 ){
					
					found = true;
					myOutputString = myTmpStr.substring(0, myStartIndex).concat(theExpression).concat( theSymbol );
					myTmpStr = myTmpStr.substring( myStartIndex + theSymbol.length(), myTmpStr.length() );
				}
				
				// --- Add the end of the line
				if ( myTmpStr != "" )
					myOutputString += myTmpStr;
					
				// --- If the tag had been found, comment the line (add '//' at the beginning of the line
				if ( found )
					myOutputString = "\n".concat(theCommentSymbol).concat(myOutputString);
				else
					// --- No symbol found, so just write the same line
					myOutputString = "\n".concat(myLine);
				
				// --- Finally add this new line to the output file
				myOutputFile.write( myOutputString.getBytes());
			}
			
		}catch (IOException e){
			System.err.println("IOException : "+e.getMessage());
		}finally {
			// --- Close the openned files
			try{
				myInputFile.close();
				myOutputFile.close();
			}catch ( Exception e ){
				; // --- Do nothing
			}
		}
	}

public static void main ( String[] args ){
		
		String myInputFile = "C:\\CAHDD\\test\\exemple.txt";
		String myOutputFile = "C:\\CAHDD\\test\\exemple2.txt";
		String theSymbol = "export(";
		String theCommentSymbol = "//";
		String theTag = "<ICI>";
		
		FindAndUpdate(myInputFile, myOutputFile,theSymbol, theCommentSymbol, theTag);
		
		
	}