在链表 (Java) 中插入值时遇到问题？

Question

Hi, I'm fairly new to LinkedLists in java and am having trouble inserting values into a linked list. The program compiles successfully and I am able to add only a few numbers to the linked list. It would help if anyone gave an explanation as to why this is happening and a solution to fixing it.

---

class LNode {
    int data;
    LNode next;
    public LNode(int data)
    {
        this.data=data;
    }
}

class linkedList {
    LNode head; // initialize head.

    // methods
    public void append(int data) {

        if(head==null) {
            head= new LNode(data);
            return;
        }
        LNode temp = head;
        while(temp.next!=null) {
            temp=temp.next; 
        }
        temp = new LNode(data);
    }

    public void prepend(int data) {
        LNode temp=new LNode(data);
        temp.next=head;
        head=temp;      
    }

    public void DelteValue(int data) {
        if(head==null)
            return;
        if(head.data==data) {
            head=head.next;
            return;
        }
        LNode current=new LNode(data);
        while(current.next!=null) {
            if(current.next.data==data) {
                current.next=current.next.next;
                return;
            }
            current=current.next;
        }

    }
    public void show() {
        LNode temp= head;
        while(temp.next!=null) {
            System.out.println(temp.data);
            temp=temp.next;
        }
    }

}

public class LinkedLists {

    public static void main(String[] args) {
        linkedList LL=new linkedList();
        LL.append(5);
        LL.append(15);
        LL.append(25);
        LL.prepend(1);
        LL.prepend(12);
        LL.prepend(22);

        LL.show();

    }
}

Please have a look and post a solution if possible? Thanks a ton.

---

Answer 1

The logic in your append() method is incorrect. After traversing to the end of the list, you need to insert the new node at the last position:

public void append(int data) {

    if (head == null) {
        head = new LNode(data);
        return;
    }

    LNode temp = head;
    while (temp.next != null) {
        temp = temp.next;
    }
    temp.next = new LNode(data);
}

Your prepend() method looks fine. I did not test your delete method, and it may have problems as well. This answer addresses directly what you asked above.

Answer 2

It's in your append method:

LNode temp = head;
while(temp.next!=null) {
   temp=temp.next; 
}
temp = new LNode(data);

When the while loop finishes, temp is pointing to the LAST thing in your list. But then you throw it out with the assignment on the next line. It should be

temp.next = new LNode(data);