组数据集成基于该值不同的子数据集

Question

我想要实现在由几列的如下所示的数据集的程序：

+-----------+---------------+-------------------+-----------------------+ 
|Item_ID |Product_Name |Manufacturer_Name |Product_Description | 
+-----------+---------------+-------------------+-----------------------+ 
|12345  |Pen   |Cello    |Ball Pen Soft Nib... | 
|12346  |Pencil   |Nataraja   |Pencil HB Extra D... | 
|42345  |Ruler   |Nataraja   |Scale No.1103 15c... | 
|12677  |Sharpener  |Nataraja   |Pencil Shraperner... | 
|12987  |Pen   |Reynolds   |Dot Pen Extra Gr... | 
|44326  |Pen   |Reynolds   |Gel Pen German T... | 
|13456  |Pen   |Cello    |Dot Pen 0.5mm Nib... | 
|19876  |Eraser   |Cello    |Dust free Eraser ... | 
|43246  |Ink Pen  |Hero    |Ink Pen Smooth Ha... | 
+-----------+---------------+-------------------+-----------------------+ 

，我想基于所述Manufacturer_Name组数据集等所示低于

Manufacturer = Cello 
+-----------+---------------+-------------------+-----------------------+ 
|Item_ID |Product_Name |Manufacturer_Name |Product_Description | 
+-----------+---------------+-------------------+-----------------------+ 
|12345  |Pen   |Cello    |Ball Pen Soft Nib... | 
|13456  |Pen   |Cello    |Dot Pen 0.5mm Nib... | 
|19876  |Eraser   |Cello    |Dust free Eraser ... | 
+-----------+---------------+-------------------+-----------------------+ 

Manufacturer = Nataraja 
+-----------+---------------+-------------------+-----------------------+ 
|Item_ID |Product_Name |Manufacturer_Name |Product_Description | 
+-----------+---------------+-------------------+-----------------------+ 
|12346  |Pencil   |Nataraja   |Pencil HB Extra D... | 
|42345  |Ruler   |Nataraja   |Scale No.1103 15c... | 
|12677  |Sharpener  |Nataraja   |Pencil Shraperner... | 
+-----------+---------------+-------------------+-----------------------+ 

Manufacturer = Reynolds 
+-----------+---------------+-------------------+-----------------------+ 
|Item_ID |Product_Name |Manufacturer_Name |Product_Description | 
+-----------+---------------+-------------------+-----------------------+ 
|12987  |Pen   |Reynolds   |Dot Pen Extra Gr... | 
|44326  |Pen   |Reynolds   |Gel Pen German T... | 
+-----------+---------------+-------------------+-----------------------+ 

Manufacturer = Hero 
+-----------+---------------+-------------------+-----------------------+ 
|Item_ID |Product_Name |Manufacturer_Name |Product_Description | 
+-----------+---------------+-------------------+-----------------------+ 
|43246  |Ink Pen  |Hero    |Ink Pen Smooth Ha... | 
+-----------+---------------+-------------------+-----------------------+ 

我尝试使用下面的代码，它不会产生好的结果。帮我改进这个程序。以下是我使用的代码：

Dataset<Row> countsBy = src.select("Manufacturer_Name").distinct(); 
List<Row> lsts = countsBy.collectAsList(); 
for (Row lst : lsts) { 
    String man = lst.toString(); 
    System.out.println("Records of " + man + " only"); 
    Dataset<Row> mandataset = src.filter("Manufacturer_Name='" + man + "'"); 
    mandataset.show(); 
} 

Answer 1

也许你可以试着让地图数据集的，关键一个字符串（MANUFACTURER_NAME）和每一次迭代中，检查MANUFACTURER_NAME，那么你检查它是否已经在地图中（如果需要，您可以创建它），最后，将您的行添加到好的数据集中。

你有类似的东西：

Map<string,ArrayList<ShopItem>> dic = new HashMap<string,ArrayList<ShopItem>>(); 
for(/*...*/) 
{ 
    string Manufacturer_Name = //you get the name 
    if(/*the Manufacturer_Name is not in dic*/) 
    { 
    dic.put(Manufacturer_Name,new ArrayList<ShopItem>()); 
    } 
    dic.get(Manufacturer_Name).Add(/*what you want to add*/); 
} 

然后你需要第二个循环，但仅用于打印数据。

我希望它能解决您的问题！

编辑：按地图（对不起）remplaced Dictionnary并提供链接

How do you create a dictionary in Java?

编辑：改变的代码匹配