class dec_runnable implements Runnable {

private ArrayList<byte[]> input;
private ArrayList<byte[]> output;
private String counter;
private byte[] key;

public dec_runnable(ArrayList<byte[]> input, String counter, byte[] key) {
   this.input = (ArrayList<byte[]>) input.clone();
   output = new ArrayList<>();
   this.counter = counter;
   this.key = new byte[key.length];
   System.arraycopy(key, 0, this.key, 0, key.length);
}

@Override
public void run() {
   try {
         Cipher cipher = Cipher.getInstance("AES/ECB/NoPadding");
         SecretKeySpec skeySpec = new SecretKeySpec(key, "AES");
         cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
         for (int i = 0; i < input.size(); i++) {
            counter = ctr_dec.increment(counter);
            byte[] c = input.get(i);
            byte[] ct = cipher.doFinal(counter.getBytes());
            byte[] m = ctr_dec.xor(c, ct);
            output.add(m);
         }
   } catch (NoSuchAlgorithmException
            | NoSuchPaddingException | InvalidKeyException
            | IllegalBlockSizeException | BadPaddingException ex) {
   }
}

public ArrayList<byte[]> getOutput() {
   return output;
}

}

class dec_thread extends Thread {

dec_runnable dr;

public dec_thread(dec_runnable dr) {
   super(dr);
   this.dr = dr;
}

public dec_runnable getDr() {
   return dr;
}
}

If a CTR mode is using the same nonce and the following are obtaine...