我在双重LinkedList中有问题,我没有使用尾巴,而是使用当前指针。当我使用尾巴时,我没有发现问题,但是当我使用当前指针时,出现了错误,并且无法解决。当我删除节点时会发生。我的程序正在运行,但是无法删除下一个节点。这是错误消息:
此类DNode
public class DNode<T> {
T data;
DNode<T> next;
DNode<T> prev;
public DNode(T e){
data = e;
next = prev = null;
}
此类DoubleLinkedList
public class DoubleLinkedList<T> {
DNode<T> head;
DNode<T> current;
int size = 0;
public DoubleLinkedList() {
head = current = null;
}
public void Insert(T e) {
DNode<T> tmp = new DNode(e);
if (size == 0) {
head = current = tmp;
} else {
tmp.next = current.next;
tmp.prev = current;
current.next = tmp;
current = tmp;
}
size++;
}
public void remove() {
if (head == current) {
if (current.next == null) {
head = current = null;
} else {
current.next.prev = null;
head = current.next;
current.next = null;
current = head;
}
} else {
DNode<T> tmp = current.next;
current.prev.next = tmp;
if (tmp != null) {
tmp.prev = current;
}
current.next = current.prev = null;
current = tmp;
}
size--;
}
主要成绩
public static void main(String[] args) {
DoubleLinkedList<String> d = new DoubleLinkedList();
d.Insert("jon");
d.Insert("jack");
d.Insert("mohammed");
d.remove();
d.remove();// here my problem
}
带有注释的行是我得到错误的地方。
在删除功能的else部分中,将电流分配给tmp。当您说current = tmp;
时,tmp可能为空。因此,下次调用remove时,如果它输入else子句(在您的情况下如此),当前将为null,并且current.next
给出null指针异常。
EDIT:这可能是一个建议:
/*Deletes the last node in the list*/
public void remove() {
if(head == null || size == 0) return; // Empty list
if(head == current || size ==1){ // List with only one node
head = null;
current = null;
size--;
return;
}
DNode<T> previous = current.prev;
previous.next = current.next;
current.prev = null;
current = previous;
size--;
}