Java - suma de niveles de un arbol

package clases;

import java.util.LinkedList;

public class TGTree<T> {

    public T info;

    public LinkedList< TGTree<T> > children;

   public TGTree(T info) {

        this.info = info;

        children = new LinkedList<>();

    }

    public TGTree(T info, LinkedList<TGTree<T>> children) {

        this.info = info;

        this.children = children;

    }

    /**

     * Es hoja

     *

     */

    public boolean iSheet() {

        if (children.size() == 0) {

            return true;

        }

        return false;

    }

}

package edapfinal;

import clases.TGTree;

import java.util.ArrayList;

public class EDAPFinal<T> {

    public static int SumaNivel(int Nivel, TGTree<Integer> ArbolEnteros) {

        if(ArbolEnteros==null){

            return 0;

        }int aux = 0;

        for (int i = 0; i < ArbolEnteros.children.size(); i++) {

            int suma=SumaNivel(Nivel-1, ArbolEnteros);

            aux=suma;

            if(Nivel ==0){

            return suma;

        }

        }

        return aux;

    }

    public static void main(String[] args) {

        // TODO code application logic here

        Stack<Integer> P1 = new Stack<>();

        Stack<Integer> P2 = new Stack<>();

        P1.push(10);

        P1.push(8);

        P1.push(5);

        P1.push(1);

        P2.push(14);

        P2.push(11);

        P2.push(9);

        System.out.println(Mezclar(P1, P2));

        TGTree a1 = new TGTree(1);

        TGTree a2 = new TGTree(2);

        TGTree a3 = new TGTree(3);

        TGTree a4 = new TGTree(4);

        TGTree a5= new TGTree(5);

        TGTree a6 = new TGTree(6);

        TGTree a7 = new TGTree(7);

        TGTree a8 = new TGTree(8);

        TGTree a9 = new TGTree(9);

        TGTree a10 = new TGTree(10);

        a1.children.add(a2);

        a1.children.add(a3);

        a2.children.add(a4);

        a3.children.add(a5);

        a3.children.add(a6);

        a3.children.add(a7);

        a5.children.add(a8);

        a6.children.add(a9);

        a6.children.add(a10);

        System.out.println(SumaNivel(2, a1));

    }

}