如何编写查找父母和孩子的递归方法 [英] How to write a recursive method for finding parent and child

问题描述

这是为了以递归方式保存详细信息.

在这里，我想从数据库中获取详细信息，并使用递归方法将其设置到我的bean中.这样我就可以在angularUi树形对象中显示.如何编写递归方法以设置到我的bean中.

Here I want to get the details from the Database and set into my bean with a recursive method. So I can dispaly in angularUi tree formate. How can I write the recursive method to set into my beans.

我的数据库严格程度:-

我使用rowId分隔父母和孩子.您可以访问我的示例屏幕.

I am separating the parents and childs with rowId.you can access my sample screen.

例如:-父级的Rowid为1 这个1的孩子是1.1 而1.1的孩子是1.1.1，这样会延长，.

Eg:- Rowid is 1 for parent the child for this 1 is 1.1 and child for 1.1 is 1.1.1 like this it will prolong,,.

我将所有父母和孩子都保存在图片上方的一张桌子中.

I am saving all the parents and child in a single table which is above image.

每个对象(行)都有items[].如果有任何子代为父，则该子代将被添加到该items[]数组中；如果该子代有任何子代，则该子代将被添加到该行的items[]父代中.

there will be items[] for each and every object(Row). If there is any child for parent then the child will be added in that items[] array, if that child have any child then the child will be added in the parent of that row's items[]... like this it will prolong.

例如:-JSON对象为:-

{
    "id": 1,
    "rowId": "1",
    "items": [
      {
        "id": 10,
        "rowId": "1.1",
        "items": [
          {
            "id": 100,
            "rowId": "1.1.1",
            "items": [
              {
                "id": 1000,
                "rowId": "1.1.1.1",
                "items": []
              }
            ]
          }
        ]
      },
      {
        "id": 11,
        "rowId": "1.2",
        "items": []
      }
    ]
  }

我已经使用但是在检索时我遇到了问题.问题是检索时不会有任何父项和子项，因为数据将保存在同一表中.该关系仅是rowid.为此，我需要编写一种类似保存的递归方法，并且需要将子级添加到父级items[]数组中.

But while retriving I am facing problems. The problem is while retrieving there will not be any parent and childs as the data will be saved in same table.The relationship is only rowid. For This I need to write a recursive method like saving, and need to add the childs to parent items[] array.

public class AdminComponentBean{

    List<MultiAdminComponent> componentListbean;
}

MultiAdminComponent.java:-

public class MultiAdminComponent {

    private String componentName;
    private String componentIdentification;
    private String componentType;
    private String componentState;
    private String componentUrl;
    private String rowId;
    private List<MultiAdminComponent> items;
}

在这里，我尝试检索所有详细信息，并尝试将子级添加到父级.但这应该是一种递归方法

Here I try to retrive all the details and trying to add the childs to parent.But it should make a recursive method

List<MultiAdminComponent> componentList=BaseDAO.getAdminComponentDAOObject().getComponentDetails();
   if(null != componentList) {
       for(MultiAdminComponent itemsList : componentList){
           if(itemsList.getRowId().length().equals() "1"){//here parent row will come
               //by considering rowid I need to find the child of the rowId
               //child of 1 is 1.1
               //if 1.1 is child of 1 then I need to add that 1.1 object to `items[]` array of 1
               //like this it should work recursve
            }
        }
    }

推荐答案

我建议不要采取递归的方式，而是将所有元素都存储在HashMap中

Instead of recursive I would suggest to go an extra step and store all elements in a HashMap

// a map containing all elements searchable by the rowId
HashMap<String, MultiAdminComponent> idToItem = new HashMap<>();
// a set containing all elements that don't have a parent (id: 1, 2, 3, etc.)
Set<MultiAdminComponent> rootItems = new HashSet<>();

for (MultiAdminComponent item : componentList) {
    // build the id->item map
    idToItem.put(item.getRowId(), item);
}

for (MultiAdminComponent item : componentList) {
    String parentId = getParentId(item.getRowId());
    if (parentId == null) {
        // this item has no parent -> it is a root item
        rootItems.add(item);
    } else {
        // This item has a parent -> look the parent up
        MultiAdminComponent parent = idToItem.get(parentId);
        parent.getItems().add(item);
    }
}

// rootItems now contains all MultiAdminComponents which do not have a parent, with the correct hierarchy for all items

getParentId可能是这样的:

getParentId could be something like this:

private String getParentId(String id) {
    int lastDot = id.lastIndexOf(".");
    if (lastDot == -1) {
        return null;
    }
    return id.substring(0, lastDot);
}

如果可以保证componentList将从父级到子级遍历整个列表，则可以将两个for循环组合在一起.

If you can guarantee that componentList will go through the list from parents to children, you can combine both for-loops.

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