import java.util.Vector;

class Item {
	public int val;
	public Vector<Item> children;
	Item(int val) {
		this.val = val;
		this.children = new Vector<Item>();
	}
	public Item addChild(int val) {
		children.add(new Item(val));
		return children.lastElement();
	}
}
public class Tree {
	public static Item root;
	public static void main(String[] args) {
		Item curr = root = new Item(0);
		curr = curr.addChild(10);
		//...
	}
}