java如何用递归生成树形结构
作者：L丶小先生
作者分享了自己在使用脚本之家资源进行编程时的经验,包括准备实体对象、测试数据、构造树形结构递归函数、测试以及输出结果等步骤,作者希望这些经验能对大家有所帮助,并鼓励大家支持脚本之家
java用递归生成树形结构
1、准备实体对象
public class TreeNode{
private int id;
private int pid;
private String name;
private String content;
private List<TreeNode> children;
public TreeNode() {
}
public TreeNode(int id, int pid, String name, String content) {
this.id = id;
this.pid = pid;
this.name = name;
this.content = content;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public int getPid() {
return pid;
}
public void setPid(int pid) {
this.pid = pid;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getContent() {
return content;
}
public void setContent(String content) {
this.content = content;
}
public List<TreeNode> getChildren(){
return children;
}
public void setChildren(List<TreeNode> children){
this.children = children;
}
@Override
public String toString() {
return "TreeNode{" +
"id=" + id +
", pid=" + pid +
", name='" + name + '\'' +
", content='" + content + '\'' +
'}';
}
}2、准备测试数据
//生成测试数据方法
public static List<TreeNode> generateList(){
List<TreeNode> list = new ArrayList<>();
TreeNode treeModel1 = new TreeNode(1,0,"系统管理",getRandomStr());
TreeNode treeModel2 = new TreeNode(11,1,"用户管理",getRandomStr());
TreeNode treeModel3 = new TreeNode(111,11,"用户添加",getRandomStr());
TreeNode treeModel4 = new TreeNode(2,0,"权限管理",getRandomStr());
TreeNode treeModel5 = new TreeNode(21,2,"账号管理",getRandomStr());
TreeNode treeModel6 = new TreeNode(221,2,"角色管理",getRandomStr());
list.add(treeModel1);
list.add(treeModel2);
list.add(treeModel3);
list.add(treeModel4);
list.add(treeModel5);
list.add(treeModel6);
return list;
}
//随便写了一个由26个小写字母随机生成字符串方法
public static String getRandomStr(){
StringBuilder ret= new StringBuilder();
for (int i = 0; i < 6; i++) {
int num=(int)(Math.random()*26+97);
ret.append((char) num);
}
return ret.toString();
}3、构造树形结构递归函数
/**
* 生成树
* @param list 待处理的数据集合
* @param pid 最顶层的父级id
*/
public static List<TreeNode> createTree(List<TreeNode> list,int pid){
//根据父id过滤出所有父节点
List<TreeNode> tree = list.stream().filter(e-> pid == e.getPid()).collect(Collectors.toList());
//遍历所有父节点，把属于该节点的所有子节点加到该节点的children属性下
for (TreeNode node: tree) {
int id = node.getId();
//过滤出所有属于该节点的子节点
List<TreeNode> cList = list.stream().filter(e-> id == e.getPid()).collect(Collectors.toList());
//判断是否存在子节点，若子节点有数据则把该子节点的id作为pid继续递归往下层处理
if(!SysUtil.isNull(cList)){
createTree(list,id);
node.setChildren(cList);
}
}
return tree;
}4、测试
public static void main(String[] args) throws Exception {
List<TreeNode> list = generateList();
list.forEach(System.out::println);
List<TreeNode> tree = createTree(list,0);
System.out.println(JSON.toJSONString(tree));
}5、输出结果
TreeNode{id=1, pid=0, name='系统管理', content='vyzjpq'}
TreeNode{id=11, pid=1, name='用户管理', content='qwbiex'}
TreeNode{id=111, pid=11, name='用户添加', content='zuyuth'}
TreeNode{id=2, pid=0, name='权限管理', content='ctgevw'}
TreeNode{id=21, pid=2, name='账号管理', content='ulgvdx'}
TreeNode{id=221, pid=2, name='角色管理', content='fzxufe'}
[{"children":[{"children":[{"content":"zuyuth","id":111,"name":"用户添加","pid":11}],"content":"qwbiex","id":11,"name":"用户管理","pid":1}],"content":"vyzjpq","id":1,"name":"系统管理","pid":0},{"children":[{"content":"ulgvdx","id":21,"name":"账号管理","pid":2},{"content":"fzxufe","id":221,"name":"角色管理","pid":2}],"content":"ctgevw","id":2,"name":"权限管理","pid":0}]
总结
以上为个人经验，希望能给大家一个参考，也希望大家多多支持脚本之家。