secure data in java https://security.stackexchange.com/questions/74718/is-it-more-secure-to-overwrite-the-value-char-in-a-string

string_erase.java

  static void clear(String source) {
    try {
      Field charField = String.class.getDeclaredField("value");
      charField.setAccessible(true);

      SecureRandom random = SecureRandom.getInstanceStrong();
      char[] noise = new char[source.length()];
      for (int i = 0; i < source.length(); i++) {
        noise[i] = (char) random.nextInt(Character.MAX_VALUE + 1);
      }
      charField.set(source, noise);
    } catch (NoSuchAlgorithmException | NoSuchFieldException | IllegalAccessException ex) {
      LOGGER.error("Failed to clear String", ex);
    }
  }