TreeUtil（树形结构转换）

雨点打透心脏的1/2处 2022-11-02 11:52 206阅读 0赞

> `TreeUtil（树形结构转换）`

> 1、Entity（实体类）

@Data
    @AllArgsConstructor
    @NoArgsConstructor
    public class RegionTree { 
    
        //id
        private String id;
    
        //父节点id
        private String parentId;
    
        //子节点
        private List<RegionTree> children;
    }

> 2、TreeUtils

import org.apache.commons.lang3.StringUtils;
    
    import java.util.ArrayList;
    import java.util.Iterator;
    import java.util.List;
    public class TreeUtil { 
        /** * 创建树结构 * * @param regionTrees 树形结构list * @return treeList */
        public static List<RegionTree> tree(List<RegionTree> regionTrees) { 
            //返回的节点树
            List<RegionTree> rootNodes = new ArrayList<>();
            Iterator<RegionTree> it = regionTrees.iterator();
            while (it.hasNext()) { 
                RegionTree next = it.next();
                //parent（上级Id）为0的是根节点
                if (StringUtils.isEmpty(next.getParentId())) { 
                    rootNodes.add(next);
                    it.remove();
                }
            }
    
            //遍历，找到二级节点
            for (RegionTree regionTree : rootNodes) { 
                List<RegionTree> child = getChild(regionTrees, regionTree.getId().toString());
                regionTree.setChildren(child);
            }
            return rootNodes;
    
        }
    
        /** * 查子节点 * * @param regions 树结构对象 * @param parentId 父id * @return treeList */
        private static List<RegionTree> getChild(List<RegionTree> regions, String parentId) { 
    
            //子节点列表
            List<RegionTree> childList = new ArrayList<>();
            Iterator<RegionTree> it = regions.iterator();
            while (it.hasNext()) { 
                RegionTree regionTree = it.next();
                if (parentId.equals(regionTree.getParentId())) { 
                    childList.add(regionTree);
                    it.remove();
                }
            }
    
            //遍历 递归获取子节点的子节点
            for (RegionTree regionTree : childList) { 
                List<RegionTree> child = getChild(regions, regionTree.getId().toString());
                regionTree.setChildren(child);
            }
    
            //递归出口 childList长度为0
            if (childList.size() == 0) { 
                return new ArrayList<>();
            }
            return childList;
        }
    }

> 3、Test

public class TestTreeUtils { 
        public static void main(String[] args) { 
            List<RegionTree> list = new ArrayList<>();
    
            RegionTree m1 = new RegionTree("1", null, null);
            RegionTree m2 = new RegionTree("2", "1", null);
            RegionTree m3 = new RegionTree("3", "2", null);
            RegionTree m4 = new RegionTree("4", "3", null);
            RegionTree m5 = new RegionTree("5", "3", null);
    
            list.add(m1);
            list.add(m2);
            list.add(m3);
            list.add(m4);
            list.add(m5);
    
            RegionTree m11 = new RegionTree("6", null, null);
            RegionTree m12 = new RegionTree("7", "6", null);
            RegionTree m13 = new RegionTree("8", "7", null);
            RegionTree m14 = new RegionTree("9", "8", null);
            RegionTree m15 = new RegionTree("10", "8", null);
    
            list.add(m15);
            list.add(m11);
            list.add(m12);
            list.add(m13);
            list.add(m14);
    
            List<RegionTree> regionTreeTree = TreeUtil.tree(list);
    
            System.out.println(regionTreeTree);
        }
    }

转载自：[https://www.jianshu.com/p/fabedd4d2884][https_www.jianshu.com_p_fabedd4d2884]

[https_www.jianshu.com_p_fabedd4d2884]: https://www.jianshu.com/p/fabedd4d2884