java判断字符串中某字符出现的位置,并替换指定指定内容

      String[] b = { "\"关羽\"", "\"刘备\"" };
        String a = “元数据”;
        for (int i = 0; i < 2; i++) {
            StringBuffer sb = new StringBuffer(a);
            int c = a.indexOf("\"actualNum\":\"\"");
            sb.replace(c+12, c + 14, b[i]);
            a = sb.toString();
            System.out.println("" + a);
        }
        System.out.println("最终结果      " + a);