code: private void save() {
      Preferences pref = Preferences
          .userNodeForPackage(ConnectionDialog.class);
  
      pref.put("host", getHost());
      pref.put("user", getUser());
  
      boolean remember = getRememberPasswordCheckBox().isSelected();
      if (remember) {
        try {
          Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
          KeyGenerator keygen = KeyGenerator.getInstance("AES");
          SecureRandom random = SecureRandom.getInstance("SHA1PRNG");
          random.setSeed(new byte[]{
            0x60, (byte) 0xFD, 0x28, 0x07, 0x35, 0x4A, 0x0D, 0x3B
          });
          byte[] iv = new byte[16];
          random.nextBytes(iv);
          IvParameterSpec spec = new IvParameterSpec(iv);
          keygen.init(128, random);
          cipher.init(Cipher.ENCRYPT_MODE, keygen.generateKey(), spec);
          byte[] clearText = getPassword().getBytes();
          byte[] cipherText = cipher.doFinal(clearText);
          pref.putByteArray("password", cipherText);
          pref.putBoolean("remember", true);
        } catch (Exception e) {
          logger.error("Could not encrypt password", e);
          pref.remove("password");
          pref.putBoolean("remember", false);
        }
      } else {
        pref.remove("password");
        pref.putBoolean("remember", false);
      }
    }
docs: Saves field values to preferences.