java如何用递归生成树形结构

目录

• Java用递归生成树形结构
• 1、准备实体对象
• 2、准备测试数据
• 3、构造树形结构递归函数
• 4、测试
• 5、输出结果
• 总结

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=" + idandroid +
				", 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 statiaCWeiinqKpc 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()).collectwww.devze.com(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='zu编程yuth'}

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&quandroidot;: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编程客栈(www.devze.com)。