try (FileInputStream fin = new FileInputStream("xxx.txt")) {
            byte[] buffer = new byte[fin.available()];
            fin.read(buffer, 0, fin.available());
            sss = new String(buffer, "cp866");
          } catch (IOException ex) {
            ex.printStackTrace();
        }

try (FileWriter writer = new FileWriter("xxx_.txt", false)) {
            writer.write(sss);
        } catch (Exception e) {
              ex.printStackTrace();
        }

try (FileInputStream fin = new FileInputStream("xxx.txt")) {
            byte[] buffer = new byte[fin.available()];
            fin.read(buffer, 0, fin.available());
            sss = new String(buffer, "cp866");
          } catch (IOException ex) {
            ex.printStackTrace();
        }

String text = FileUtils.readFileToString(file, "cp866");
FileUtils.writeStringToFile(anotherFile, "UTF-8");

ry (FileInputStream fin = new FileInputStream("xxxx.txt")) {
            byte[] buffer = new byte[fin.available()];
            fin.read(buffer, 0, fin.available());
            sss = new String(buffer, "cp866");
            System.out.println(" --------- " + sss.indexOf("ЛАЛАЛА"));
//            System.out.println(sss);
        } catch (IOException ex) {
            ex.printStackTrace();
        }

Returns an estimate of the number of remaining bytes that can be read (or skipped over) from this input 
stream without blocking by the next invocation of a method for this input stream. Returns 0 when the file position is 
beyond EOF. The next invocation might be the same thread or another thread. A single read or skip of this many bytes
 will not block, but may read or skip fewer bytes.
In some cases, a non-blocking read (or skip) may appear to be blocked when it is merely slow, for example when reading large files over slow networks.
Возвращает:
an estimate of the number of remaining bytes that can be read (or skipped over) from this input stream without blocking.