1 LinkedList
public class LinkedList<E> extends AbstractSequentialList<E> implements List<E>, Deque<E>, Cloneable, java.io.Serializable
实现原理,通过双向链表实现的。适合插入、删除操作。
2 节点
LinkedList使用双向链表实现,而双向链表通过节点来实现,我们来看看节点的定义。
private static class Node<E> { E item; Node<E> next; Node<E> prev; Node(Node<E> prev, E element, Node<E> next) { this.item = element; this.next = next; this.prev = prev; } }
3 元素操作
LinkedList默认大小为0,没有扩容机制,每增加一个元素,容量加1。
(1) add
public boolean add(E e) { linkLast(e); return true; }
void linkLast(E e) { final Node<E> l = last; final Node<E> newNode = new Node<>(l, e, null); last = newNode; if (l == null) first = newNode; else l.next = newNode; size++; modCount++; }
(2) remove
public E remove(int index) { checkElementIndex(index); return unlink(node(index)); }
E unlink(Node<E> x) { // assert x != null; final E element = x.item; final Node<E> next = x.next; final Node<E> prev = x.prev; if (prev == null) { first = next; } else { prev.next = next; x.prev = null; } if (next == null) { last = prev; } else { next.prev = prev; x.next = null; } x.item = null; size--; modCount++; return element; }
(3) get
public E get(int index) { checkElementIndex(index); return node(index).item; }
Node<E> node(int index) { // assert isElementIndex(index); if (index < (size >> 1)) { Node<E> x = first; for (int i = 0; i < index; i++) x = x.next; return x; } else { Node<E> x = last; for (int i = size - 1; i > index; i--) x = x.prev; return x; } }
4、其他方法
getFirst()
getLast()
addFirst()
addLast()
removeFirst()
removeLast()