Doubly linked list java remove - linked-list

Question

I have a problem when deleting many nodes.
I can delete them if I select nodes like this:
But if I do something like this, I cannot delete them:
My Code:
public boolean remove(ProductNode<E> data) {
if (isEmpty()) {
throw new NoSuchElementException();
}
for (ProductNode<E> current = this.head; current != null; current = current.next) {
ProductNode<E> pre = current.prev;
ProductNode<E> next = current.next;
if (data != null) {
if (current.data.equals(data.data)) {
if (pre == null) {
head = next;
current.next = null;
} else {
if (next != null) {
next.prev = pre;
}
}
if (next == null) {
pre.next = null;
current.prev = null;
tail = pre;
} else {
if (pre != null) {
pre.next = next;
}
}
}
}
}
size--;
return false;
}
Search node
public ProductNode<E> search(E data) {
for (ProductNode<E> current = this.head; current != null; current = current.next) {
if (current.data.equals(data)) {
return current;
}
}
return null;
}
Remove
public void remove(E e) {
remove(search(e));
}
Delete:
for(Tab_Product p : remove_list){
List_Products.list_products.remove(p);
}

Answer 1

Your remove function (ProductNode data), is a bit complicated and may be affecting your code's ability to delete multiple nodes. In the case of this remove function you do not need traverse the whole data set. If you already have a reference to the node you can just directly modify the list with it.
public boolean remove(ProductNode<E> data) {
if (isEmpty()) {
throw new NoSuchElementException();
}
ProductNode<E> pre = data.prev;
ProductNode<E> next = data.next;
//First remove the nodes references to its neighbors.
data.prev = null;
data.next = null;
// Now check the neighbors and update their references
// to remove all references to the deleted node.
if (pre != null) pre.next = next;
if (next != null) next.prev = pre;
if (data == head) { //This checks the actual memory address.
head = next;
}
size--;
}
Since you already have the ProductNode, you do not need to search the list. your search() function is already doing that for you. since you already have the node you just need to make its references to its neighbors null then you just have to access the neighbors (if there are any) and make their old references skip over the deleted node.
I noticed a few reference errors where a deleted node was not getting completely removed from the list but i will not mention them because this delete function is rather complicated. Try simplifying the delete function and then see what your results are.
It also might be helpful if you show us the structure of the List_Products object.
Additionally you should verify that the data you select in the UI is getting passed correctly. This could be a UI bug.