Java数据结构——双向链表

什么是双向链表？
每一个结点不仅配有next引用，同时还有一个prev引用，指向其上一个结点（前驱结点）， 没有前驱的时候就为NULL。

（以下图片均来自网络，侵删）

与单链表的区别？
和单向链表相比有以下优势：

1. 插入删除不需要移动元素外，可以原地插入删除
2. 可以双向遍历

插入操作

删除操作

实现

public class DLNode {
Object data;
DLNode prev;
DLNode next;
static DLNode head;
static DLNode tail;

// 无参构造
public DLNode() {
super();
}

// 有参构造
public DLNode(Object data, DLNode prev, DLNode next) {
super();
this.data = data;
this.prev = prev;
this.next = next;
}

// 获取数据
public Object getData() {
return data;
}

// 修改数据
public void setData(Object data) {
this.data = data;
}

// 得到前驱结点
public DLNode getPrev() {
return prev;
}

// 修改前驱结点
public void setPrev(DLNode prev) {
this.prev = prev;
}

// 获取后驱结点
public DLNode getNext() {
return next;
}

// 修改后驱结点
public void setNext(DLNode next) {
this.next = next;
}

// 获取长度
public static int getLength() {
int count = 0;
for (DLNode n = head; n != null; n = n.next) {
count++;
}
return count;
}

// 插入结点
public static void add(Object data, int index) {
DLNode node = new DLNode(data, null, null);
if (index == 0) {
node.next = head;
node.prev = null;
head = node;
} else if (index == getLength()) {
tail.next = node;
node.prev = tail;
tail = node;

} else {
int temp = 0;
for (DLNode n = head; n != null; n = n.next) {
temp++;
if (temp == index) {
node.next = n.next;
n.next.prev = node;
n.next = node;
node.prev = n;
break;
}
}
}
}

//删除结点
public static void remove(int index) {
if (index == 0) {
head = head.next;
head.prev = null;
} else if (index == getLength() - 1) {
tail = tail.prev;
tail.next = null;
} else if (index >= getLength()) {
System.out.println("超出链表长度");
System.exit(0);
} else {
int temp = 0;
for (DLNode n = head; n != null; n = n.next) {
temp++;
if (temp == index) {
n.next = n.next.next;
n.next.prev = n;
break;
}
}
}
}

public static void main(String[] args) {
DLNode node1 = new DLNode("aaa", null, null);
DLNode node2 = new DLNode("bbb", node1, null);
DLNode node3 = new DLNode("ccc", node2, null);
DLNode node4 = new DLNode("ddd", node3, null);
node3.setNext(node4);
node2.setNext(node3);
node1.setNext(node2);
head = node1;
tail = node4;
System.out.print("当前链表：");
for (DLNode n = head; n != null; n = n.next) {
System.out.print(n.data + " ");
}
System.out.println();
System.out.println("链表长度：" + getLength());
add("eee", 4);
System.out.print("插入后链表：");
for (DLNode n = head; n != null; n = n.next) {
System.out.print(n.data + " ");
}
System.out.println();
remove(0);
System.out.print("删除后链表：");
for (DLNode n = head; n != null; n = n.next) {
System.out.print(n.data + " ");
}
}
}