替换模板字符串中的变量
    如 $amount$元$amountName$
    根据输入参数 amount 1999 amountName 红包
    输出 1999元红包

    2.     public static String replaceTemplateParams(String templateContent, Map<String, String> extMap) {
    3.         List<String> paramList = pickDynamicParamList(templateContent);
    4.         StringBuilder stringBuilder = new StringBuilder();
    5.         int startIndex = 0;
    6.         for (String param : paramList) {
    7.             String value = extMap.get(StringUtil.trim(param, '$'));
    8.             if (StringUtils.isBlank(value)) {
    9.                 value = "";
    10.             }
    11.             int index = templateContent.indexOf(param, startIndex);
    12.             stringBuilder.append(templateContent, startIndex, index);
    13.             stringBuilder.append(value);
    14.             startIndex = index + param.length();
    15.         }
    16.         stringBuilder.append(templateContent.substring(startIndex));
    17.         return stringBuilder.toString();
    18.     }
    20.     private static List<String> pickDynamicParamList(String templateContent) {
    21.         List<String> result = Lists.newArrayList();
    22.         int startIndex = 0;
    23.         int endIndex = 0;
    24.         boolean enterDynamic = false;
    25.         char[] chars = templateContent.toCharArray();
    26.         for (int i = 0; i < chars.length; i++) {
    27.             if ('$' != chars[i]) {
    28.                 continue;
    29.             }
    30.             if (!enterDynamic) {
    31.                 startIndex = i;
    32.                 enterDynamic = true;
    33.             } else {
    34.                 endIndex = i;
    35.                 enterDynamic = false;
    36.             }
    37.             if (!enterDynamic) {
    38.                 String params = String.valueOf(Arrays.copyOfRange(chars, startIndex, endIndex + 1));
    39.                 result.add(params);
    40.             }
    41.         }
    42.         return result;
    43.     }
    45.     public static String trim(String str, char c) {
    46.         char[] chars = str.toCharArray();
    47.         int len = chars.length;
    48.         int st = 0;
    49.         while ((st < len) && (chars[st] == c)) {
    50.             st++;
    51.         }
    52.         while ((st < len) && (chars[len - 1] == c)) {
    53.             len--;
    54.         }
    55.         return (st > 0) && (len < chars.length) ? str.substring(st, len) : str;
    56.     }
    58.     public static void main(String[] args) {
    59.         String templateContent = "$amount$元$amountName$";
    60.         Map<String, String> extMap = new HashMap<>();
    61.         extMap.put("amount", "1999");
    62.         extMap.put("amountName", "红包");
    63.         System.out.println(replaceTemplateParams(templateContent, extMap));
    64.     }