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transient int size = 0;// 链表长度transient Nodefirst;// 头节点transient Node last; //尾节点# 可以看出这是一个双向链表//构造函数public LinkedList(Collection c) { this(); addAll(c); }public boolean addAll(Collection c) { return addAll(size, c); }// 以size为下标 从尾部追加public boolean addAll(int index, Collection c) { checkPositionIndex(index);// 越界校验 Object[] a = c.toArray(); //集合转为数组 int numNew = a.length; if (numNew == 0) return false;// 空 返回false Node pred, succ;// index的前置 后置节点 if (index == size) { // 在size尾部追加节点 succ = null; pred = last; } else { succ = node(index); //取index为后置节点 pred = succ.prev; } for (Object o : a) { @SuppressWarnings("unchecked") E e = (E) o; Node newNode = new Node<>(pred, e, null); if (pred == null)//如果前驱节点为空 新节点为头节点 first = newNode; else pred.next = newNode; //前置节点的后置设置为新节点 pred = newNode; //指针移动下一步 } if (succ == null) { last = pred;//后置为空 则新节点为尾节点 } else { //中间插入 前后节点设置 pred.next = succ; succ.prev = pred; } // 修改链表长度 size += numNew; // 修改次数+1 modCount++; return true; }// 二分思想 Node node(int index) { // assert isElementIndex(index); if (index < (size >> 1)) { Node x = first; for (int i = 0; i < index; i++) x = x.next; return x; } else { Node x = last; for (int i = size - 1; i > index; i--) x = x.prev; return x; } }
小结
Node节点类
private static class Node{ E item;// 元素值 Node next;// 后置节点 Node prev;// 前驱节点 Node(Node prev, E element, Node next) { this.item = element; this.next = next; this.prev = prev; } }
// 从尾部添加public boolean add(E e) { linkLast(e); return true; }void linkLast(E e) { final Nodel = last;// l为尾节点引用 final Node newNode = new Node<>(l, e, null); //构造新节点 last = newNode;//新节点置为尾节点 if (l == null) //空链表 first = newNode; //置为头节点 else l.next = newNode; //原尾节点l的后置变成当前节点 size++; modCount++; }
//指定index 插入元素public void add(int index, E element) { checkPositionIndex(index);// 校验是否越界 if (index == size)//若index等于链表长度 追加至尾节点 linkLast(element); else linkBefore(element, node(index)); }succ节点前插入新节点void linkBefore(E e, Nodesucc) { // assert succ != null; //保存后置节点的前置节点 final Node pred = succ.prev; // 构造新节点 final Node newNode = new Node<>(pred, e, succ); // succ的前置节点为新节点 succ.prev = newNode; if (pred == null)// 空链表 新节点置为头节点 first = newNode; else pred.next = newNode;//前置节点的后置为新接单 size++; modCount++;// 修改modCount }
// 插入头节点public void addFirst(E e) { linkFirst(e); }private void linkFirst(E e) { final Nodef = first;//保存原头节点 final Node newNode = new Node<>(null, e, f);// 构造新节点 first = newNode;/新节点单置为头节点 if (f == null) last = newNode;// 链表空 头尾同节点 else f.prev = newNode;// 原头节点的前置变为当前节点 size++; modCount++; }
// 移除头节点public E remove() { return removeFirst(); }public E removeFirst() { final Nodef = first; if (f == null) throw new NoSuchElementException(); return unlinkFirst(f); }private E unlinkFirst(Node f) { // assert f == first && f != null; final E element = f.item; 保存头节点的值 final Node next = f.next;//获取头节点的后置 f.item = null; f.next = null; // help GC 去掉引用 first = next; //后置next置为头节点 if (next == null) last = null;//只有一个头节点 尾节点置空 else next.prev = null; //next节点的前置置空 size--; modCount++; return element; }
public E remove(int index) { checkElementIndex(index);// 越界校验 return unlink(node(index)); }E unlink(Nodex) { // assert x != null; final E element = x.item; final Node next = x.next; final Node prev = x.prev; if (prev == null) { // 前置为空 first = next; //next为头节点 } else { prev.next = next;// 断开前置与x的关联 x.prev = null; //x的前置引用断开 } if (next == null) { //后置节点为空 当前节点为尾节点 last = prev; } else { next.prev = prev;//后置的前置引用指向x的前置 x.next = null; //断开后置的引用 } x.item = null; //当前元素置空 size--; //修改size modCount++; //修改modCount return element; }
// 移除指定节点public boolean remove(Object o) { if (o == null) { //允许元素为null for (Nodex = first; x != null; x = x.next) { if (x.item == null) { unlink(x); return true; } } } else { for (Node x = first; x != null; x = x.next) { if (o.equals(x.item)) { unlink(x); return true; } } } return false; }
public E set(int index, E element) { checkElementIndex(index);// 越界校验 Nodex = node(index); E oldVal = x.item; //将原元素的值替换为新元素 x.item = element; return oldVal; }
public E get(int index) { checkElementIndex(index); //判断越界 return node(index).item; //根据index获取值 }
public Object[] toArray() { Object[] result = new Object[size]; //构造一个size大小的数组 int i = 0; for (Nodex = first; x != null; x = x.next) result[i++] = x.item; //遍历每个元素放到数组中 return result; }
public boolean offer(E e) { //布尔返回值 添加成功true return add(e); }
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