package linklist;

public class IntDLList {
    private IntDLLNode head, tail;
    public IntDLList() {
        head = tail = null;
    }
    public boolean isEmpty() {
        return head == null;
    }
    public void setToNull() {
        head = tail = null;
    }

    public int headData() {
        if (!isEmpty())
             return head.data;
        else return 0;
    }

    public void addToHead(int el) {
        if (!isEmpty()) {
             head = new IntDLLNode(el,head,null);
             head.next.prev = head;
        }
        else head = tail = new IntDLLNode(el);
    }
    public void addToTail(int el) {
        if (!isEmpty()) {
             tail = new IntDLLNode(el,null,tail);
             tail.prev.next = tail;
        }
        else head = tail = new IntDLLNode(el);
    }
    public void deleteFromHead() {
        if (!isEmpty()) {        // if at least one node in the list;
             if (head == tail)   // if only one node in the list;
                  head = tail = null;
             else {              // if more than one node in the list;
                  head = head.next;
                  head.prev = null;
             }
        }
    }
    public void deleteFromTail() {
        if (!isEmpty()) {
             if (head == tail)   // if only one node on the list;
                  head = tail = null;
             else {              // if more than one node in the list;
                  tail = tail.prev;
                  tail.next = null;
             }
        }
    }
    public void printAll() { //OutputStream Out) {
        for (IntDLLNode tmp = head; tmp != null; tmp = tmp.next)
             System.out.print(tmp.data + " ");
    }
    public int find(int el) {
        IntDLLNode tmp;
        for (tmp = head; tmp != null && tmp.data != el; tmp = tmp.next);
        if (tmp == null)
             return 0;
        else return tmp.data;
    }
}