java - 只打印链表的最后两个值

Question

这是我的 Node 类

public class listNode {
String data;
listNode next;

     public listNode(String data, listNode next) {
        this.data = data;
        this.next = next;
     }       

     public String toString(){
        return data;
     }
}

她是我的列表类

public class List {
listNode head;

    public List(){
        head = null;
    }

    public void addLast(String target){
        if(head == null){
            head = new listNode(target,head);
        }
        while(head.next != null){
            head = head.next;
        }
        head.next = new listNode(target,null);
    } 
}

打印方法:

public void print(){
    while(head != null){
        System.out.println(head.toString());
        head = head.next;
    }
}

当我在主函数中使用这个方法时，它总是只打印链表的最后两个值，我很困惑。

示例:

l1.addLast("a");
l1.addLast("b");
l1.addLast("c");

它只打印

b,c

Answer 1

下面的代码是错误的。您不应该更改头部对象。使用不同的对象。

while(head.next != null){
            head = head.next;
}

应该是这样的:

class List {
listNode head;

    public List(){
        head = null;
    }

    public void addLast(String target){
        if(head == null){
            head = new listNode(target,head);
        }
        else {
            listNode last = head;
            while(last.next != null){
                last = last.next;
            }
            last.next = new listNode(target,null);  
        }

    } 
}