线性表的链式存储结构之单链表类的实现_Java

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package dataStructure.linearList;
import dataStructure.linearList.Node; //导入单链表结点类
public class SinglyLinkedList<E> implements LList<E> //单链表类，实现线性表接口
{
protected Node<E> head; //头指针，指向单链表第一个结点
public SinglyLinkedList() //构造空单链表
{
this.head = null;
}
public SinglyLinkedList(Node<E> head) //构造指定头指针的单链表
{
this.head = head;
}
public boolean isEmpty() //判断单链表是否为空
{
return this.head == null;
}
public int length() //返回单链表长度，单链表遍历算法
{
int i = 0;
Node<E> p = this.head;
while(p != null)
{
i ++;
p = p.Next;
}
return i;
}
public E get(int index) //返回序号为index的对象，若单链表为空或序号错误则返回null
{
if(this.head != null && index >= 0)
{
int j = 0;
Node<E> p = this.head;
while(p != null && j < index)
{
j ++;
p = p.Next;
}
if(p !=null)
{
return (E)p.Data;
}
}
return null;
}
public E set(int index,E element) //设置序号为index的对象为element，若操作成功，返回原对象，否则返回null
{
if(this.head != null && index >= 0 && element != null)
{
int j = 0;
Node<E> p = this.head;
while(p != null && j < index)
{
j ++;
p = p.Next;
}
if(p != null)
{
E old = (E)p.Data;
p.Data = element;
return old; //若操作成功，则返回原对象
}
}
return null; //操作不成功
}
public boolean add(int index,E element) //插入element对象，插入后对象序号为index，若操作成功返回true
{
if(element ==null)
{
return false; //不能添加空对象(null)
}
if(this.head == null || index <= 0) //头插入
{
Node<E> q = new Node<E>(element);
q.Next = this.head;
this.head = q;
//this.head = new Node(element,this.head); //头插入，相当于上述3句
}
else //单链表不空且index>=1
{
int j = 0;
Node<E> p = this.head;
while(p.Next != null && j < index - 1) //寻找插入位置
{
j ++;
p = p.Next;
}
Node<E> q = new Node<E>(element); //中间/尾插入
q.Next = p.Next; //q插入在p结点之后
p.Next = q;
//p.Next = new Node(element,p.Next); //中间/尾插入，相当于上述3句
}
return true;
}
public boolean add(E element) //在单链表最后插入对象
{
return add(Integer.MAX_VALUE,element);
}
public E remove(int index) //移去序号为index的对象，若操作成功则返回被移去的对象，否则返回null
{
E old = null;
if(this.head != null && index >= 0)
{
if(index == 0) //头删除
{
old = (E)this.head.Data;
this.head = this.head.Next;
}
else //中间/尾删除
{
int j = 0;
Node<E> p = this.head;
while(p.Next != null && j < index - 1) //定位到待删除结点的前驱结点
{
j ++;
p = p.Next;
}
if(p.Next != null)
{
old = (E)p.Next.Data; //若操作成功，返回被移去对象
p.Next = (p.Next).Next; //删除p的后继结点
}
}
}
return old;
}
public void clear() //清空单链表
{
this.head = null;
}
public String toString() //返回所有元素值对应的字符串
{
String str = "(";
Node<E> p = this.head;
while(p != null)
{
str += p.Data.toString();
p = p.Next;
if(p != null)
{
str += ",";
}
}
return str + ")";
}
}