Method removeFirst

12_LinkedList.java/DoubleLL.java:42–59

()

    //remove - removeLast
    public int removeFirst() {
        if(head == null) {
            System.out.println("DLL is empty");
            return Integer.MIN_VALUE;
        }

        if(size == 1) {
            int val = head.data;
            head = tail = null;
            size--;
            return val;
        }
        int val = head.data;
        head = head.next;
        head.prev = null; 
        size--;
        return val;
    }

    public void reverse() {
        Node curr = head;