public Song[] swapSongs(Song[] list, int a, int b)
    {
        Song tmp = list[a];
        list[a] = list[b];
        list[b] = tmp;
        return list;
    }

    public static void main(String[] args)
    {
        Node n = new Node(3);
        Song s1 = new Song(); s1.setTitle("B");
        Song s2 = new Song(); s2.setTitle("A");
        n.push(s1); n.push(s2);
        
        System.out.println("Data: \n"+s1+"\n"+s2+"\n");
        System.out.println("Sorting...\n");
        //n.sortNode();
        n.data = n.swapSongs(n.data,0,1);
        System.out.println("Swapped data: \n"+s1+"\n"+s2);
    }


The output:
Data: 
B
A

Sorting...

Swapped data: 
B
A