java版本 递归树形结构的源代码

以下是 Java 版本的递归树形结构的源代码：

public class TreeNode {
    private int val;
    private TreeNode left;
    private TreeNode right;

    public TreeNode(int val) {
        this.val = val;
        this.left = null;
        this.right = null;
    }

    public void insert(int val) {
        if (val < this.val) {
            if (this.left == null) {
                this.left = new TreeNode(val);
            } else {
                this.left.insert(val);
            }
        } else {
            if (this.right == null) {
                this.right = new TreeNode(val);
            } else {
                this.right.insert(val);
            }
        }
    }

    public void printInOrder() {
        if (this.left != null) {
            this.left.printInOrder();
        }
        System.out.print(this.val + " ");
        if (this.right != null) {
            this.right.printInOrder();
        }
    }
}

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