public interface Set<E> extends Collection<E>

public interface Queue<E> extends Collection<E>

public class HashMap<K,V>
    extends AbstractMap<K,V>
    implements Map<K,V>, Cloneable, Serializable

public class LinkedList<E>
    extends AbstractSequentialList<E>
    implements List<E>, Deque<E>, Cloneable, java.io.Serializable

/**
 * The array buffer into which the elements of the ArrayList are stored.
 * The capacity of the ArrayList is the length of this array buffer. Any
 * empty ArrayList with elementData == EMPTY_ELEMENTDATA will be expanded to
 * DEFAULT_CAPACITY when the first element is added.
  数组中包含的元素。
 */
private transient Object[] elementData;

/**
 * The size of the ArrayList (the number of elements it contains).
 * 这个list的中包含的元素的个数。
 */
private int size;