public class Node {
    private int id;
    private int parentId;
    private List<Node> children;

    // 構(gòu)造函數(shù)、Getter和Setter省略
}

import java.util.ArrayList;
import java.util.List;

public class TreeUtils {

    /**
     * 遞歸查詢一個(gè)節(jié)點(diǎn)下的所有子節(jié)點(diǎn)ID
     * @param rootNode 起始節(jié)點(diǎn)
     * @return 所有子節(jié)點(diǎn)的ID列表
     */
    public static List<Integer> findAllChildNodeIds(Node rootNode) {
        List<Integer> childNodeIds = new ArrayList<>();
        addAllChildNodeIds(rootNode, childNodeIds);
        return childNodeIds;
    }

    private static void addAllChildNodeIds(Node node, List<Integer> childNodeIds) {
        if (node == null) {
            return;
        }
        List<Node> children = node.getChildren();
        if (children != null) {
            for (Node child : children) {
                childNodeIds.add(child.getId());
                addAllChildNodeIds(child, childNodeIds); // 遞歸調(diào)用
            }
        }
    }
}

public class Main {
    public static void main(String[] args) {
        // 構(gòu)造節(jié)點(diǎn)關(guān)系
        Node root = new Node();
        root.setId(1);
        
        Node child1 = new Node();
        child1.setId(2);
        
        Node child2 = new Node();
        child2.setId(3);
        
        root.setChildren(Arrays.asList(child1, child2));
        
        // 查詢所有子節(jié)點(diǎn)ID
        List<Integer> allChildNodeIds = TreeUtils.findAllChildNodeIds(root);
        
        // 輸出結(jié)果
        System.out.println("All Child Node IDs: " + allChildNodeIds);
    }
}