Java - 从 LinkedList 中删除一个元素，除了 first

Question

I'm new to Java.

I have created a method where it will remove elements from LinkedList except the first one. The idea is a boolean will be set to true if a LinkedList's element data (Which is in Integer) matched with parameter. Once the boolean sets to true, it will remove any element that also matched with initial one.

Now for the problem. For example, if I were to remove 5 except the first one from this LinkedList:

5 5 5 6 5 7 8 9

I will get result like this:

5 5 6 7 8 9

As you can see, it didn't remove the 5 on the second position. Is there anything wrong with my code?

Here's the code by the way

public void append(int data) {
    Node newNode = new Node(data);
    if (head == null) {
        head = new Node(data);
        return;
    }

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

    lastNode.next = newNode;
    return;
}

public void insert(int data) {
    Node newData = new Node(data);
    newData.next = head;
    head = newData;
}

public void removeExceptFirst(int dataValue) { //The mentioned method
    boolean duplicate = false;
    Node currentNode = head;
    while (currentNode.next != null) {
        int value = currentNode.next.data;
        if (value == dataValue) {
            if (!duplicate) {
                duplicate = true;
                currentNode = currentNode.next;
            } else {
                currentNode.next = currentNode.next.next;
            }
        } else {
        currentNode = currentNode.next;
        }
    }
    return;
}

Answer 1

The problem here is with

if (!duplicate) {
     duplicate = true;
     currentNode = currentNode.next;
} 

you are marking duplicate = true and immediately assigning the "currentNode = currentNode.next;" due to this reference is getting preserve of the next node So

1. Put the condition outside of the loop to check whether the head element itself is 
   that node, if->yes mark isDuplicate = true and proceed in the loop.
2. Inside the loop check afterward and then assign the next node.

Hope this should work

Answer 2

You skipped head node. Try replace

    Node currentNode = head;

with

    Node currentNode = new Node();
    currentNode.next = head;

Answer 3

You should update the current node reference as well as head->next should point to the current node after removing the node. try the below code:

if (!duplicate) {
    duplicate = true;
    currentNode = currentNode.next;
     head.next= currentNode.next;
}else {
    currentNode.next = currentNode.next.next;
    currentNode = currentNode.next;
    head.next = currentNode;  }

`