docs: public static boolean isNumber(String pString) {
          if (isEmpty(pString)) {
              return false;
          }
  
          // Special case for first char, may be minus sign ('-')
          char ch = pString.charAt(0);
          if (!(ch == '-' || Character.isDigit(ch))) {
              return false;
          }
  
          // Test every char
          for (int i = 1; i < pString.length(); i++) {
              if (!Character.isDigit(pString.charAt(i))) {
                  return false;
              }
          }
  
          // All digits must be a natural number
          return true;
      }