java中双向链表的增删改查

public class DoubleLinkedDemo {

public static void main(String[] args) {
	// TODO Auto-generated method stub
	//打印结点
	StuNode stu1=new StuNode("钢铁侠","1000");
	StuNode stu2=new StuNode("白","1001");
	StuNode stu3=new StuNode("鸣人","1002");
	StuNode stu4=new StuNode("佐助","1003");
	StuNode stu5=new StuNode("美国队长","1004");
	//创建链表
	DoubleLinked Link=new DoubleLinked();
	Link.add(stu1);
	Link.add(stu2);
	Link.add(stu3);
	Link.add(stu4);
	Link.add(stu5);
	Link.show();
	//按照学号修改元素，则学号保持不变
	System.out.println();
	StuNode stu6=new StuNode("绿巨人","1004");
	Link.update(stu6);
	Link.show();
	//删除结点，根据姓名
	System.out.println();
	Link.del("绿巨人");
	Link.show();
}

}

class StuNode{

protected String name;
protected String num;
protected StuNode next;
protected StuNode pre;

public StuNode(String name,String num) {
	this.name=name;
	this.num=num;
}

public String toString() {
	return name+" - " +num;
}	
}

class DoubleLinked{
//创建头节点结点
private StuNode head=new StuNode("","");

public StuNode getHeda() {
	return head;
}
//尾插法添加元素
public void add(StuNode stu) {
	StuNode temp=head;
	while(temp.next!=null) {
		temp=temp.next;
	}
	temp.next=stu;
	stu.pre=temp;
}
//删除元素
public void del(String name) {
	if(head.next==null) {
		System.out.println("双向链表为空");
	}
	StuNode temp=head.next;
	boolean flag=false;
	while(temp!=null) {
		if(temp.name==name) {
			flag=true;
			break;
		}
		temp=temp.next;
	}
	if(flag) {
		temp.pre.next=temp.next;
		//若没有if判断 则删除最后一个元素的时候会出现空指针异常
		if(temp.next!=null)
		temp.next.pre=temp.pre;
	}else
	{
		System.out.println("此元素不存在");
	}
}
//改元素,根据学号查找
public void update(StuNode stu) {
	if(head.next==null)		{
		System.out.println("双向列表为空");
		return;
	}
	StuNode temp=head.next;
	boolean flag=false;
	while(temp!=null) {
		if(temp.num==stu.num) {
			flag=true;
			break;
		}
		temp=temp.next;
	}
	if(flag) {
		temp.name=stu.name;
		temp.num=stu.num;
	}else {
		System.out.println("双向链表里未找到相应的学号，跟新失败");
	}
}
//查找元素，根据姓名查找
public boolean search(String name) {
	if(head.next==null) {
		System.out.println("双向链表为空");
		return false;
	}
	StuNode temp=head.next;
	boolean flag=false;
	while(temp!=null) {
		if(temp.name==name) {
			flag=true;
		}
		temp=temp.next;
	}
	return flag;
}
//打印链表
public void show() {
	StuNode temp=head.next;
	while(temp!=null) {
		System.out.println(temp);
		temp=temp.next;
	}
}
}