APS Prv kolokvium

import java.util.Scanner;
public class DvojnaLista {
    public static void main(String [] args) {
        Scanner input = new Scanner(System.in);
        //citanje na broj na elementi
        int m = input.nextInt();
        int n = input.nextInt();
        DLL<Integer> lista1 = new DLL<Integer>();
        DLL<Integer> lista2 = new DLL<Integer>();
        DLL<Integer> lista3 = new DLL<Integer>();
        //citaj listi, edna po edna
        for (int i = 0; i < m; i++) {
            int el = input.nextInt();
            lista1.insertLast(el);
        }
        for (int i = 0; i < n; i++) {
            int el = input.nextInt();
            lista2.insertLast(el);
        }
        //vasiot kod tuka ...
        DLLNode<Integer> attempt1 = lista1.getLast();
        DLLNode<Integer> attempt2 = lista2.getFirst();

        while(attempt1!=null && attempt2!=null) {
            if((int)attempt2.element > (int)attempt1.element) {
                lista3.insertLast(attempt2.element);
                attempt2 = attempt2.succ;
            }
            else if((int)attempt1.element > (int)attempt2.element) {
                lista3.insertLast(attempt1.element);
                attempt1 = attempt1.pred;
            }
        else if(attempt1.element == attempt2.element) {
                lista3.insertLast(attempt1.element);
                lista3.insertLast(attempt2.element);
                attempt1 = attempt1.pred;
                  attempt2 = attempt2.succ;
            }
        }
        if(attempt1!=null) {
            while(attempt1!=null) {
                lista3.insertLast(attempt1.element);
                attempt1 = attempt1.pred;
            }
        }
        if(attempt2!=null) {
            while(attempt2!=null) {
                lista3.insertLast(attempt2.element);
                attempt2 = attempt2.succ;
            }
        }
        //pecatenje
        System.out.println(lista3.toString());
        System.out.println(lista3.toStringR());
    }
}
class DLLNode<E> {
    protected E element;
    protected DLLNode<E> pred, succ;
    public DLLNode(E elem, DLLNode<E> pred, DLLNode<E> succ) {
        this.element = elem;
        this.pred = pred;
        this.succ = succ;
    }
    @Override
    public String toString() {
        return element.toString();
    }
}
class DLL<E> {
    private DLLNode<E> first, last;
    public DLL() {
        // Construct an empty SLL
        this.first = null;
        this.last = null;
    }
    public void deleteList() {
        first = null;
        last = null;
    }
    public int length() {
        int ret;
        if (first != null) {
            DLLNode<E> tmp = first;
            ret = 1;
            while (tmp.succ != null) {
                tmp = tmp.succ;
                ret++;
            }
            return ret;
        } else
            return 0;
    }
    public DLLNode<E> find(E o) {
        if (first != null) {
            DLLNode<E> tmp = first;
            while (tmp.element != o && tmp.succ != null)
                tmp = tmp.succ;
            if (tmp.element == o) {
                return tmp;
            } else {
                System.out.println("Elementot ne postoi vo listata");
            }
        } else {
            System.out.println("Listata e prazna");
        }
        return first;
    }
    public void insertFirst(E o) {
        DLLNode<E> ins = new DLLNode<E>(o, null, first);
        if (first == null)
            last = ins;
        else
            first.pred = ins;
        first = ins;
    }
    public void insertLast(E o) {
        if (first == null)
            insertFirst(o);
        else {
            DLLNode<E> ins = new DLLNode<E>(o, last, null);
            last.succ = ins;
            last = ins;
        }
    }
    public void insertAfter(E o, DLLNode<E> after) {
        if(after==last){
            insertLast(o);
            return;
        }
        DLLNode<E> ins = new DLLNode<E>(o, after, after.succ);
        after.succ.pred = ins;
        after.succ = ins;
    }
    public void insertBefore(E o, DLLNode<E> before) {
        if(before == first){
            insertFirst(o);
            return;
        }
        DLLNode<E> ins = new DLLNode<E>(o, before.pred, before);
        before.pred.succ = ins;
        before.pred = ins;
    }
    public E deleteFirst() {
        if (first != null) {
            DLLNode<E> tmp = first;
            first = first.succ;
            if (first != null) first.pred = null;
            if (first == null)
                last = null;
            return tmp.element;
        } else
            return null;
    }
    public E deleteLast() {
        if (first != null) {
            if (first.succ == null)
                return deleteFirst();
            else {
                DLLNode<E> tmp = last;
                last = last.pred;
                last.succ = null;
                return tmp.element;
            }
        }// else throw Exception
        return null;
    }
    public E delete(DLLNode<E> node) {
        if(node==first){
            deleteFirst();
            return node.element;
        }
        if(node==last){
            deleteLast();
            return node.element;
        }
        node.pred.succ = node.succ;
        node.succ.pred = node.pred;
        return node.element;
    }
    @Override
    public String toString() {
        String ret = new String();
        if (first != null) {
            DLLNode<E> tmp = first;
            ret += tmp + "<->";
            while (tmp.succ != null) {
                tmp = tmp.succ;
                ret += tmp + "<->";
            }
        } else
            ret = "Prazna lista!!!";
        return ret;
    }
    public String toStringR() {
        String ret = new String();
        if (last != null) {
            DLLNode<E> tmp = last;
            ret += tmp + "<->";
            while (tmp.pred != null) {
                tmp = tmp.pred;
                ret += tmp + "<->";
            }
        } else
            ret = "Prazna lista!!!";
        return ret;
    }
    public DLLNode<E> getFirst() {
        return first;
    }
    public DLLNode<E> getLast() {
        return last;
    }
    public void izvadiDupliIPrebroj(){
    }
}