实现list interface

又是面经啊，不知道意义何在，摘从library：
对于list这个借口，要注意的是list里的元素是有序的，可以按index存，取

package java.util;
public interface List<E> extends Collection<E> {
    int size();
    boolean isEmpty();

    //Returns an array containing all of the elements in this list in proper sequence (from first to last element).
    Object[] toArray();
    <T> T[] toArray(T[] a);

    //Appends the specified element to the end of this list (optional operation).
    boolean add(E e);
    void add(int index, E element);
    boolean addAll(Collection<? extends E> c);
    boolean addAll(int index, Collection<? extends E> c);
    E get(int index);
    E set(int index, E element);
    int indexOf(Object o);
    int lastIndexOf(Object o);


    //Removes the first occurrence of the specified element from this list, if it is present (optional operation).
    boolean remove(Object o);
    E remove(int index);
    boolean removeAll(Collection<?> c);
    
    //Retains only the elements in this list that are contained in the specified collection (optional operation).
    boolean retainAll(Collection<?> c);

    //Returns true if this list contains the specified element.
    boolean contains(Object o);
    boolean containsAll(Collection<?> c);
    
    void clear();
    boolean equals(Object o);
    int hashCode();

    ListIterator<E> listIterator();

    //Returns a list iterator over the elements in this list (in proper sequence), starting at the specified position in the list.
    ListIterator<E> listIterator(int index);
    
    // Returns an iterator over the elements in this list in proper sequence.
    Iterator<E> iterator();

    //Returns a view of the portion of this list between the specified fromIndex, inclusive, and toIndex, exclusive.
    List<E> subList(int fromIndex, int toIndex);
}