code: public static String getRandomText(int floor, int ceil, int length) {
          StringBuilder builder = new StringBuilder();
          for (int i = 0; i < length; i++) {
              builder.append((char) getRandomInteger(floor, ceil));
          }
          return builder.toString();
      }
docs: 获取自定义随机字符串
  
  @param floor ascii下限
  @param ceil ascii上限
  @param length 长度
  
  @return 字符串