Java three-level menu tool class implementation method

Java general three-level menu tool class

Usually, when writing a third-level menu, you will use recursive methods to write, but over time, you will find that many duplicate codes are being written and changed, and only a few names are changed.

Implementation method

Abstract property structure

The three commonly used fields are child id, parent id, and the second is array children.

This class will be implemented by returning an object or a third-level menu object.

import ;
public interface AbstractTreeNode {
    // Child id    Long getId();
    // Parent id    Long getParentId();
    // Child array    void setChildren(List&lt;? extends AbstractTreeNode&gt; children);
}

Code Example

import ;
import ;
import ;
@Data
public class ForumBoardVo implements AbstractTreeNode {
    private Long id;
    // Parent section ID    private Long parentId;
    // Section name    private String boardName;
    // Cover    private String cover;
    // describe    private String boardDesc;
    // Sort    private Integer sort;
    // 0: Only administrators are allowed to post 1: Anyone can post    private Boolean postType;
    private List&lt;ForumBoardVo&gt; children;
    @Override
    public void setChildren(List&lt;? extends AbstractTreeNode&gt; children) {
         = (List&lt;ForumBoardVo&gt;) children;
    }
}

Building a tree structure

import ;
import ;
public class TreeBuilder&lt;T extends AbstractTreeNode&gt; {
    /**
      * Build attribute structure
      *
      * @param nodeList The array to be built
      * @return Tree structure
      */
    public List&lt;T&gt; buildTree(List&lt;T&gt; nodeList) {
        List&lt;T&gt; tree = new ArrayList&lt;&gt;();
        for (T node : nodeList) {
            if (() == 0) {
                (getChildren((), nodeList));
                (node);
            }
        }
        return tree;
    }
    /**
      * Recursively set the child menu
      *
      * @param nodeId nodeid
      * @param nodeList node list
      * @return child menu
      */
    private List&lt;T&gt; getChildren(Long nodeId, List&lt;T&gt; nodeList) {
        List&lt;T&gt; children = new ArrayList&lt;&gt;();
        for (T node : nodeList) {
            if (().equals(nodeId)) {
                (getChildren((), nodeList));
                (node);
            }
        }
        return children;
    }
}

First, return the array to normal. After all, we want to return the VO object. If we directly return the object in the database, it is also OK. Let's only give an example below.

public List&lt;ForumBoardVo&gt; loadBoard() {
    // list in the database    List&lt;ForumBoard&gt; forumBoardListDB = list();
    // Build return object array    List&lt;ForumBoardVo&gt; forumBoardVoList = new ArrayList&lt;&gt;();
    // Tree structure returns an array    TreeBuilder&lt;ForumBoardVo&gt; treeBuilder = new TreeBuilder&lt;&gt;();
    // Sort the arrays in the database, this is optional    ((ForumBoard::getSort));
    // Fill the arrays in the database into the array of List<ForumBoardVo> one by one    (forumBoard -&gt; {
        ForumBoardVo forumBoardVo = new ForumBoardVo();
        (forumBoard, forumBoardVo);
        (forumBoardVo);
    });
    // Finally, the tree structure object will be called to build a tree structure.    return (forumBoardVoList);
}

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