/**
 * This interface describes a simple list with operations
 * to add and remove elements from either end of the list.
 *
 * @param <E> type of elements stored in the list
 */
public interface SimpleList<E> {
    /**
     * Adds the given element to the start of the list.
     * @param elem element to add
     */
    public void addFirst(E elem);

    /**
     * Adds the given element to the end of the list.
     * @param elem element to add
     */
    public void addLast(E elem);

    /**
     * Removes the first element from the list.
     * @return element that was removed
     * @throws NoSuchElementException if there is no first element
     */
    public E removeFirst();

    /**
     * Removes the last element from the list.
     * @return element that was removed
     * @throws NoSuchElementException if there is no last element
     */
    public E removeLast();

    /**
     * Returns the size of the list (i.e. the number of elements
     * stored in the list.
     * @return size of list
     */
    public int size();

    /**
     * Returns the element in the list at the given index.
     * @param index index of element to return
     * @return element at given index
     * @throws IndexOutOfBoundsException if given index is invalid
     */
    public E get(int index);

    /**
     * Returns the list as a string. The string contains all of the elements
     * in order from first to last.
     * @return list as a string
     */
    public String toString();

    /**
     * Returns true of this list is equal to the given list.
     * Two lists are equal if they contain the same elements in the same order.
     * @param otherList list to compare to this list
     * @return true if lists are equal
     */
    public boolean equals(SimpleList<E> otherList);
}