public static void simpleReplace(String file, String oldChar, String newChar){
		FileReader fr = null;
		PrintWriter pw = null;
		File f = new File(file);
		boolean b = f.exists();
		boolean fileNotEmpty = true;
		try{
			fr = new FileReader(file + ".txt");
			BufferedReader br = new BufferedReader(fr);
			if (b) {
				pw = new PrintWriter(new FileWriter(file + ".txt", true));
			}
			else {
				pw = new PrintWriter(new FileWriter(file + ".txt", false));
			}
			while (fileNotEmpty){
				String s = br.readLine();
				if (s == null)
				{
					fileNotEmpty = false;
					break;
				}
				s.toLowerCase();
				for (int i=0; i<s.length(); i++){
					oldChar = s.substring(i-1,i);
					s.replaceAll(oldChar,newChar);
					pw.println(s);
					pw.flush();
				}
				fr.close();
			}
		}
		catch(FileNotFoundException e){
			System.out.println("File not found.");
		}
		catch (IOException e) {
			e.printStackTrace();
		}
		finally {
			if (pw != null){
				pw.close();
			}
		}
	}