I'm having problems with DFS backtracking in an adjacency matrix. Here's my code: (i added the test to the main in case someone wants to test it)

public class Graph {

    private int numVertex;
    private int numEdges;
    private boolean[][] adj;

    public Graph(int numVertex, int numEdges) {
        this.numVertex = numVertex;
        this.numEdges = numEdges;
        this.adj = new boolean[numVertex][numVertex];
    }

    public void addEdge(int start, int end){
        adj[start-1][end-1] = true;
        adj[end-1][start-1] = true;
    }

    List<Integer> visited = new ArrayList<Integer>();

    public Integer DFS(Graph G, int startVertex){
        int i=0;

        if(pilha.isEmpty())
            pilha.push(startVertex);

        for(i=1; i<G.numVertex; i++){
            pilha.push(i);
            if(G.adj[i-1][startVertex-1] != false){
                G.adj[i-1][startVertex-1] = false;
                G.adj[startVertex-1][i-1] = false;
                DFS(G,i);
                break;
            }else{
                visited.add(pilha.pop());
            }
            System.out.println("Stack: " + pilha);
        }
        return -1;
    }

    Stack<Integer> pilha = new Stack();

    public static void main(String[] args) {

        Graph g = new Graph(6, 9);

        g.addEdge(1, 2);
        g.addEdge(1, 5);
        g.addEdge(2, 4);
        g.addEdge(2, 5);
        g.addEdge(2, 6);
        g.addEdge(3, 4);
        g.addEdge(3, 5);
        g.addEdge(4, 5);
        g.addEdge(6, 4);

        g.DFS(g, 1);    

    }
}

I'm trying to solve the euler path problem. the program solves basic graphs but when it needs to backtrack, it just does not do it. I think the problem might be in the stack manipulations or in the recursive dfs call. I've tried a lot of things, but still can't seem to figure out why it does not backtrack. Can somebody help me ?