java 生成树形结构_Java后台生成树状结构工具类
importjava.util.ArrayList;importjava.util.HashMap;importjava.util.List;importjava.util.Map;public classTreeUtil {//private static String PID = "000000";
/*** 将平行的树，转化为一颗有层级关系的树
*@paramlist
*@parampId
*@return
*/
public static List getTreeList(Listlist,String pId){if (list == null){return null;
}//获取所有头节点
List rootNode = new ArrayList<>();for(TreeData treeData: list ){if(treeData.getId().equals(pId)){
rootNode.add(treeData);
}
}//头节点不存在的情况
if (rootNode.size() == 0){returngetChild(pId,list);
}//头节点存在的情况
for(TreeData treeData : rootNode){
String id=treeData.getId();
treeData.setChild(getChild(id,list));
}returnrootNode;
}private static List getChild(String id,Listlist){//找到id节点子节点
List childList = new ArrayList<>();for(TreeData treeData: list){if(treeData.getpId().equals(id)){
childList.add(treeData);
}
}//给子节点设置子节点
for(TreeData treeData : childList){
id=treeData.getId();//递归
treeData.setChild(getChild(id,list));
}if (childList.size() == 0){return null;
}returnchildList;
}/*** 获取指定层级的树
*@paramtreeList
*@paramlevel
*@return
*/
public static List getTreeNodeOnLevel(List treeList,intlevel){if (treeList == null && treeList.size() == 0){return new ArrayList<>();
}
ArrayList treeListOnLevel = new ArrayList<>();//调用递归方法
treeList = TreeUtil.recursionQueryTree(treeList, treeListOnLevel, 0,level);returntreeList;
}/*** 递归查所有指定层级的树节点
*@paramtreeList
*@paramtreeListOnLevel
*@paramcurrentLevel
*@paramlevel
*@return
*/
private static List recursionQueryTree(List treeList,List treeListOnLevel,int currentLevel,intlevel){
currentLevel++;//递归循环查询指定层级树
for(TreeData treeData : treeList){if (currentLevel ==level){
treeListOnLevel.add(treeData);continue;
}//递归
if (treeData.getChild() == null || treeData.getChild().size() == 0){continue;
}
recursionQueryTree(treeData.getChild(),treeListOnLevel,currentLevel,level);
}returntreeListOnLevel;
}/*** 统计一颗树的深度
*@paramtreeList
*@return
*/
public static int getTreeLevel(ListtreeList){if (treeList == null || treeList.size() == 0){return 0;
}//调用递归统计方法
return TreeUtil.recursionCount(treeList,0,0);
}private static int recursionCount(List treeList,int currentlevel,intmaxlevel){
currentlevel++;//当当前层级大于目前最大层级时覆盖
if (currentlevel >maxlevel){
maxlevel=currentlevel;
}//递归遍历节点
for(TreeData treeData : treeList){//如果子节点为空不进行递归
if (treeData.getChild() == null || treeData.getChild().size() == 0){continue;
}//递归
maxlevel =recursionCount(treeData.getChild(), currentlevel, maxlevel);
}returnmaxlevel;
}/*** 获取指定id在此树中的层级位置
*
*@paramlist 要遍历的树
*@paramid 要寻找的节点Id
*@paramrankCount 层级统计器，传入0即可
*@return
*/
public static Map getNode(Listlist,String id,Integer rankCount){
TreeData node= null;//计数器加一
rankCount++;
Map map = new HashMap<>();
map.put("node",node);
map.put("rankCount",rankCount);//如果传入的树为0或返回层级0
if (list == null || list.size() == 0){
map.put("rankCount",0);returnmap;
}//遍历树
for(TreeData treeData : list){if(treeData.getId().equals(id)){
map.put("node",treeData);returnmap;
}if (treeData.getChild() == null || treeData.getChild().size() == 0){continue;
}//递归
Map map1 =getNode(treeData.getChild(),id,rankCount);if (map1.get("node") != null){returnmap1;
}
}//如果传入的节点是不存在的，返回层级0
map.put("rankCount",0);returnmap;
}
}