code: private String getSymbolExceptions() {
          if (TextUtils.isEmpty(filteredMask)) return "";
  
          StringBuilder maskSymbolException = new StringBuilder();
          for (char c : filteredMask.toCharArray()) {
              if (!Character.isDigit(c) && maskSymbolException.indexOf(String.valueOf(c)) == -1) {
                  maskSymbolException.append(c);
              }
          }
          maskSymbolException.append(replacementChar);
          return maskSymbolException.toString();
      }
docs: Generate symbol exception for inputType = number