Сортирање со меурчиња кај листа

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

class DLLNode<E> {
    protected E element;
    protected DLLNode<E> predecessor, successor;

    public DLLNode(E element, DLLNode<E> predecessor, DLLNode<E> successor) {
        this.element = element;
        this.predecessor = predecessor;
        this.successor = successor;
    }
}

class DLL<E> {
    private DLLNode<E> first, last;

    public DLL() {
        first = last = null;
    }

    public void insertFirst(E o) {
        DLLNode<E> insert = new DLLNode<E>(o, null, first);
        if(first == null)
            last = insert;
        else first.predecessor = insert;
        first = insert;
    }

    public void insertLast(E o) {
        if(first == null)
            insertFirst(o);
        else {
            DLLNode<E> insert = new DLLNode<E>(o, last, null);
            last.successor = insert;
            last = insert;
        }
    }

    public DLLNode<E> getFirst() {
        return first;
    }
}

public class BubbleSortLL {
    static void bubbleSort(DLL<Integer> lista) {
        DLLNode<Integer> current = lista.getFirst();

        while(current != null) {
            DLLNode<Integer> tmp = current;
            while(tmp != null) {
                if(current.element > tmp.element) {
                    int temp = current.element;
                    current.element = tmp.element;
                    tmp.element = temp;
                }
                tmp = tmp.successor;
            }
            current = current.successor;
        }

        current = lista.getFirst();
        while(current != null) {
            System.out.print(current.element + " ");
            current = current.successor;
        }
    }

    public static void main(String[] args) throws IOException {
        DLL<Integer> lista = new DLL<Integer>();

        BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in));
        String s = stdin.readLine();
        int N = Integer.parseInt(s);
        s = stdin.readLine();
        String[] pomniza = s.split(" ");
        for (int i = 0; i < N; i++) {
            lista.insertLast(Integer.parseInt(pomniza[i]));
        }

        bubbleSort(lista);
    }
}