java如何用遞歸生成樹形結構

更新時間：2025年03月04日 08:54:12 作者：L丶小先生

作者分享了自己在使用腳本之家資源進行編程時的經(jīng)驗,包括準備實體對象、測試數(shù)據(jù)、構造樹形結構遞歸函數(shù)、測試以及輸出結果等步驟,作者希望這些經(jīng)驗能對大家有所幫助,并鼓勵大家支持腳本之家

java用遞歸生成樹形結構

1、準備實體對象

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、準備測試數(shù)據(jù)

//生成測試數(shù)據(jù)方法
public static List<TreeNode> generateList(){
	List<TreeNode> list = new ArrayList<>();
	TreeNode treeModel1 = new TreeNode(1,0,"系統(tǒng)管理",getRandomStr());
	TreeNode treeModel2 = new TreeNode(11,1,"用戶管理",getRandomStr());
	TreeNode treeModel3 = new TreeNode(111,11,"用戶添加",getRandomStr());
	TreeNode treeModel4 = new TreeNode(2,0,"權限管理",getRandomStr());
	TreeNode treeModel5 = new TreeNode(21,2,"賬號管理",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;
}

//隨便寫了一個由26個小寫字母隨機生成字符串方法
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、構造樹形結構遞歸函數(shù)

/**
 * 生成樹
 * @param list 待處理的數(shù)據(jù)集合
 * @param pid 最頂層的父級id
 */
public static List<TreeNode> createTree(List<TreeNode> list,int pid){
	//根據(jù)父id過濾出所有父節(jié)點
	List<TreeNode> tree = list.stream().filter(e-> pid == e.getPid()).collect(Collectors.toList());
	//遍歷所有父節(jié)點，把屬于該節(jié)點的所有子節(jié)點加到該節(jié)點的children屬性下
	for (TreeNode node: tree) {
		int id = node.getId();
		//過濾出所有屬于該節(jié)點的子節(jié)點
		List<TreeNode> cList = list.stream().filter(e-> id == e.getPid()).collect(Collectors.toList());
		//判斷是否存在子節(jié)點，若子節(jié)點有數(shù)據(jù)則把該子節(jié)點的id作為pid繼續(xù)遞歸往下層處理
		if(!SysUtil.isNull(cList)){
			createTree(list,id);
			node.setChildren(cList);
		}
	}
	return tree;
}

4、測試

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、輸出結果

TreeNode{id=1, pid=0, name='系統(tǒng)管理', content='vyzjpq'}
TreeNode{id=11, pid=1, name='用戶管理', content='qwbiex'}
TreeNode{id=111, pid=11, name='用戶添加', content='zuyuth'}
TreeNode{id=2, pid=0, name='權限管理', content='ctgevw'}
TreeNode{id=21, pid=2, name='賬號管理', content='ulgvdx'}
TreeNode{id=221, pid=2, name='角色管理', content='fzxufe'}
[{"children":[{"children":[{"content":"zuyuth","id":111,"name":"用戶添加","pid":11}],"content":"qwbiex","id":11,"name":"用戶管理","pid":1}],"content":"vyzjpq","id":1,"name":"系統(tǒng)管理","pid":0},{"children":[{"content":"ulgvdx","id":21,"name":"賬號管理","pid":2},{"content":"fzxufe","id":221,"name":"角色管理","pid":2}],"content":"ctgevw","id":2,"name":"權限管理","pid":0}]