### 实现
~~~
public class LinkedList<E> {
private class Node {
public E e;
public Node next;
public Node(E e, Node next) {
this.e = e;
this.next = next;
}
public Node(E e) {
this(e, null);
}
public Node() {
this(null, null);
}
@Override
public String toString() {
return e.toString();
}
}
private Node dummyHead; //存储链表头
private int size; //记录容量
public LinkedList() {
dummyHead = new Node(null, null); //虚拟头
size = 0;
}
//获取链表中的元素个数
public int getSize() {
return size;
}
//返回链表是否为空
public boolean isEmpty() {
return size == 0;
}
//在链表的index(0-based)位置添加新的元素e .索引在链表中不是一个常用的操作,仅仅是练习用
public void add(int index, E e) {
if(index < 0 || index > size)
throw new IllegalArgumentException("Add failed . Illegal index.");
Node prve = dummyHead;
for(int i = 0; i < index; i++) {
prve = prve.next;
}
prve.next = new Node(e, prve.next);
size++;
}
//在链表头添加新的元素e
public void addFirst(E e) {
add(0, e);
}
//在链表末尾添加新的元素e
public void addLast(E e) {
add(size, e);
}
//获取链表的第index(0-based)个位置的元素 . 在链表中不是一个常用的操作,练习用
public E get(int index) {
if(index < 0 || index >= size)
throw new IllegalArgumentException("Get failed. Illegal index.");
Node cur = dummyHead.next;
for(int i = 0; i < index; i++) {
cur = cur.next;
}
return cur.e;
}
//获取链表第一个元素
public E getFirst() {
return get(0);
}
//获取链表最后一个元素
public E getLast() {
return get(size - 1);
}
//修改链表的第index(0-based)个位置的元素e .在链表中不是一个常用的操作,练习用
public void set(int index, E e) {
if(index < 0 || index >= size)
throw new IllegalArgumentException("Update failed. Illegal index.");
Node cur = dummyHead.next;
for(int i = 0; i < index; i++) {
cur = cur.next;
}
cur.e = e;
}
//查找链表中是否有元素e
public boolean contains(E e) {
Node cur = dummyHead.next;
while(cur != null) {
if(cur.e.equals(e)) {
return true;
}
cur = cur.next;
}
return false;
}
//从链表中删除index(0-based)位置的元素,返回删除的元素 .练习用
public E remove(int index) {
if(index < 0 || index >= size)
throw new IllegalArgumentException("Remove failed. index is index.");
Node prve = dummyHead;
for(int i = 0; i < index; i++) {
prve = prve.next;
}
Node retNode = prve.next;
prve.next = retNode.next;
retNode.next = null;
size--;
return retNode.e;
}
//从链表中删除第一个元素,返回删除元素
public E removeFirst() {
return remove(0);
}
//从链表中删除最后一个元素,返回删除元素
public E removeLast() {
return remove(size - 1);
}
//遍历链表元素
@Override
public String toString() {
StringBuilder res = new StringBuilder();
// Node cur = dummyHead.next;
// while(cur != null) {
// res.append(cur + "->");
// cur = cur.next;
// }
for(Node cur = dummyHead.next; cur != null; cur = cur.next) {
res.append(cur + "->");
}
res.append("NULL");
return res.toString();
}
}
~~~
