
![image](https://user-images.githubusercontent.com/12162539/50417924-d6cc2b80-0863-11e9-860f-bf9d132db570.png)

final StringBuilder ladderSB = new StringBuilder();
        int deep = 0;
        for (String item : items) {
            
            if (deep == 0) {
                ladderSB
                        .append(item)
                        .append("\n");
            }
            
            else {
                ladderSB
                        .append(repeat(STEP_CHAR, deep * INDENT_STEP))
                        .append(LADDER_CHAR)
                        .append(item)
                        .append("\n");
            }
            deep++;
        }
        return ladderSB.toString();
    }
    /**
     * add one item
     */
    public TLadder addItem(String item) {
        items.add(item);
        return this;
    }
}