code: @Override
      public final void readBlank() {
          char ch = nextGoodChar();
          if (ch == ':') return;
          StringBuilder sb = new StringBuilder();
          sb.append(ch);
          char one;
          try {
              while ((one = nextChar()) != 0) sb.append(one);
          } catch (Exception e) {
          }
          throw new ConvertException("expected a ':' but '" + ch + "'(position = " + position + ") in (" + sb + ")");
      }
docs: 判断下一个非空白字符是否: