JAVA-简单树形结构

野性酷女 2022-02-04 12:11 285阅读 0赞

package com.qh.health.service;
    
    import com.alibaba.fastjson.JSON;
    import com.google.common.collect.Lists;
    import com.google.common.collect.Maps;
    import lombok.Data;
    
    import java.util.List;
    import java.util.Map;
    
    /**
     * @author wzx
     * @since 2019-05-07
     */
    @Data
    public class NodeTest  {
    
        private Long id;
    
        private String name;
    
        private Long parentId;
    
        private List<NodeTest> children;
    
        public NodeTest(Long id, String name, Long parentId) {
            this.id = id;
            this.name = name;
            this.parentId = parentId;
        }
    
        public static void main(String[] args) {
            List<NodeTest> nodes = Lists.newArrayList();
            nodes.add(new NodeTest(1L, "一级", -1L));
            nodes.add(new NodeTest(2L, "一级-1", 1L));
            nodes.add(new NodeTest(3L, "一级-1-1", 2L));
            nodes.add(new NodeTest(4L, "二级", -1L));
    
            System.out.println(JSON.toJSONString(getTree(nodes)));
        }
    
        private static List<NodeTest> getTree(List<NodeTest> nodes) {
            Map<Long, NodeTest> nodeMap = Maps.newHashMap();
            List<NodeTest> rootList = Lists.newArrayList();
            for (NodeTest node : nodes) {
                nodeMap.put(node.getId(), node);
                Long parentId = node.getParentId();
                if (parentId == null || parentId <= 0) {
                    rootList.add(node);
                }
            }
            for (NodeTest node : nodes) {
                Long parentId = node.getParentId();
                if (parentId == null || parentId <=0) {
                    continue;
                }
                NodeTest pnode = nodeMap.get(parentId);
                if (pnode == null) {
                    continue;
                }
                List<NodeTest> children = pnode.getChildren();
                if (children == null) {
                    children = Lists.newArrayList();
                    pnode.setChildren(children);
                }
                children.add(node);
            }
            return rootList;
        }
    
    }

输出结果：

[{
    	"children": [{
    		"children": [{
    			"id": 3,
    			"name": "一级-1-1",
    			"parentId": 2
    		}],
    		"id": 2,
    		"name": "一级-1",
    		"parentId": 1
    	}],
    	"id": 1,
    	"name": "一级",
    	"parentId": -1
    }, {
    	"id": 4,
    	"name": "二级",
    	"parentId": -1
    }]