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This article Xiaobian introduces in detail for you "java tree structure stream tool class how to use", the content is detailed, the steps are clear, the details are handled properly, I hope this "java tree structure stream tool class how to use" article can help you solve doubts, the following follow the editor's ideas slowly in-depth, together to learn new knowledge.

Menu entity class

Package com.example.demo.entity; import lombok.AllArgsConstructor;import lombok.Builder;import lombok.Data;import lombok.NoArgsConstructor;import java.util.List;@Data@Builder@AllArgsConstructor@NoArgsConstructorpublic class Menu {/ * id * / public Integer id; * name public String name; * parent id, root node is 0 public Integer parentId; * child node information public List childList Public Menu (Integer id, String name, Integer parentId) {this.id = id; this.name = name; this.parentId = parentId;}}

Spanning tree structure utility class

Package com.example.demo.util; import cn.hutool.json.JSONUtil;import com.example.demo.entity.Menu;import java.util.Arrays;import java.util.List;import java.util.Objects;import java.util.stream.Collectors Public class TreeUtil {/ * Recursive query child node * * @ param root root node * @ param all all nodes * @ return root node information * / public static List getChildrens (Menu root, List all) {List children = all.stream () .filter (m-> {return Objects.equals (m.getParentId (), root.getId () }) .map ((m)-> {m.setChildList (getChildrens (m, all)); return m;}) .return children (Collectors.toList ()) } * @ param parentId parent node id * @ param menus menu collection * @ return returns the descendant node tree structure with id equal to parentId (excluding nodes with id equal to parentId) public static List getTree (Integer parentId, List menus) {/ / get parent node List tree = menus.stream () .filter (m-> Objects.equals (parentId) M.getParentId ()) .map (m.setChildList (getChildrens (m, menus)) Return tree; public static void main (String... Args) {/ / simulate queries from the database List menus = Arrays.asList (new Menu (1, "0-1", 0), new Menu (2, "0-1-2", 1), new Menu (3, "0-1-2-3", 2), new Menu (4, "0-1-2-4") ), new Menu (5, "0-1-2-5", 2), new Menu (6, "0-6", 0), new Menu (7, "0-6-7", 6), new Menu (8, "0-6-8", 6), new Menu (9, "0-6-7-9", 7) New Menu (10, "0-6-7-10", 7), new Menu (11, "0-11", 0), new Menu (12, "0-11-12", 11)) List tree = getTree (1menus); System.out.println ("- convert json output result -"); System.out.println (JSONUtil.parseArray (tree) .toString ()) } after reading this, the article "how to use the java Tree structure stream tool Class" has been introduced. If you want to master the knowledge points of this article, you still need to practice and use it yourself. If you want to know more about related articles, welcome to follow the industry information channel.

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