将树形结构转成json格式的java代码

假设我们有如下的树形结构：

Root
|- Node1
|  |- Node1.1
|  |- Node1.2
|     |- Node1.2.1
|     |- Node1.2.2
|- Node2
   |- Node2.1
   |- Node2.2

我们可以定义一个Java类来表示树节点：

public class TreeNode {
    private String name;
    private List<TreeNode> children;

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

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

    // getter and setter methods
}

然后，我们可以使用递归的方式将树形结构转成JSON格式的字符串：

public static String treeToJson(TreeNode node) {
    StringBuilder sb = new StringBuilder();
    sb.append("{");

    sb.append("\"name\": \"" + node.getName() + "\",");
    sb.append("\"children\": [");

    for (int i = 0; i < node.getChildren().size(); i++) {
        TreeNode child = node.getChildren().get(i);
        sb.append(treeToJson(child));

        if (i < node.getChildren().size() - 1) {
            sb.append(",");
        }
    }

    sb.append("]");
    sb.append("}");

    return sb.toString();
}

最后，我们可以使用以下代码来测试：

public static void main(String[] args) {
    TreeNode root = new TreeNode("Root");

    TreeNode node1 = new TreeNode("Node1");
    TreeNode node11 = new TreeNode("Node1.1");
    TreeNode node12 = new TreeNode("Node1.2");
    TreeNode node121 = new TreeNode("Node1.2.1");
    TreeNode node122 = new TreeNode("Node1.2.2");

    node1.addChild(node11);
    node1.addChild(node12);
    node12.addChild(node121);
    node12.addChild(node122);

    TreeNode node2 = new TreeNode("Node2");
    TreeNode node21 = new TreeNode("Node2.1");
    TreeNode node22 = new TreeNode("Node2.2");

    node2.addChild(node21);
    node2.addChild(node22);

    root.addChild(node1);
    root.addChild(node2);

    String json = treeToJson(root);
    System.out.println(json);
}

输出结果为：

{
    "name": "Root",
    "children": [
        {
            "name": "Node1",
            "children": [
                {
                    "name": "Node1.1",
                    "children": []
                },
                {
                    "name": "Node1.2",
                    "children": [
                        {
                            "name": "Node1.2.1",
                            "children": []
                        },
                        {
                            "name": "Node1.2.2",
                            "children": []
                        }
                    ]
                }
            ]
        },
        {
            "name": "Node2",
            "children": [
                {
                    "name": "Node2.1",
                    "children": []
                },
                {
                    "name": "Node2.2",
                    "children": []
                }
            ]
        }
    ]
}