java实现树形菜单

Java可以通过使用递归和面向对象的思想来实现树形菜单。面是一个简单的示例：

首先，我们需要定义一个树类，该类包含节点的值和子节点列表：

class TreeNode {
    private String value;
    private List<TreeNode> children;

    public TreeNode(String value) {
        this.value = value;
        this.children = new ArrayList<>();
    }

    public void addChild(TreeNode child) {
        children.add(child);
    }

    public List<TreeNode> getChildren {
        return children;
    }

    public String getValue() {
        return value    }
}

然后，我们可以创建一个树形菜单类，该类包含根节点和一些操作方法：

class TreeMenu {
    private TreeNode root;

    public TreeMenu(TreeNode root) {
        this.root = root;
    }

    public void printMenu() {
        printNode(root, 0);
    }

    private void printNode(TreeNode node, int level) {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < level; i++) {
            sb.append("  "); // 每一层缩进两个空格
        }
        sb.append(node.getValue());
        System.out.println(sb.toString());

        List<TreeNode> children = node.getChildren();
        for (TreeNode child : children) {
            printNode(child, level + 1);
        }
    }
}

最后，我们可以使用上述类来创建树形菜单并打印出来：

public class Main {
    public static void main(String[] args) {
        TreeNode root = new TreeNode("Root");
        TreeNode node1 = new TreeNode("Node 1");
        TreeNode node2 = new TreeNode("Node 2");
        TreeNode node3 = new TreeNode("Node 3");
        TreeNode node11 = new TreeNode("Node 1.1");
        TreeNode node12 = new TreeNode("Node 1.2");
        TreeNode node21 = new TreeNode("Node 2.1");

        root.addChild(node1);
        root.addChild(node2);
        root.addChild(node3);
        node1.addChild(node11);
        node1.addChild(node12);
        node2.addChild(node21);

        TreeMenu treeMenu = new TreeMenu(root);
        treeMenu.printMenu();
    }
}

运行上述代码，将会输出以下树形菜单：

Root
  Node 1
    Node 1.1
    Node 1.2
  Node 2
    Node 2.1
  Node 3