链接列表从尾部删除

Question

I am trying to remove at the end from a singly Linked List.I don't have a tail variable which keeps reference to the last item on the list..Therefore this is my implementation.My question is after while loop if I set current=null; it doesn't work(It doesn't remove the last node).I have to set current.next=null; .
But what do I have to add next for current.next=null; .Even if I say current=null; doesn't that mean point the node current to null.Can someone please explain why I have to use next there?

public void removeFromTail() throws EmptyStackException{
        if(head==null){
            throw new EmptyStackException("can't delete .Empty list");}
        else if(head.next==null){
            head=null;
        }
        else{
            ListNode current=head;
            while(current.next.next!=null){
                current=current.next;
            }


        current.next=null;}
}

Answer 1

When you do current=null; you set the (local) variable current to null , but still the same object is pointed in your list, you want the object in the list which points to the last object with his next member ( someobject.next ) to stop pointing there, so you need to change the value of someobject.next , eg someobject.next = null;

Answer 2

current is a reference to the current position in your linked list. After the while loop, current refers to the second to last item. When you say current.next = null , you make the current object's next become null . That makes the current object the last object.

When you say current = null , you are just setting your local reference variable to null . In other words, it no longer refers to your list. It refers to null .

Answer 3

Why not use remove method of List interface?

LinkedList<String> sss = new LinkedList<String>();
sss.add("a");
sss.add("b");
sss.remove(sss.size() - 1); // removes "b"