i need help with the insert method, i can't get it working if the timestamp is lesser than the current

public class DoubleList
{
private DoubleNode head;
private DoubleNode tail;

public DoubleList()
{
head = null;
tail = null;
}

public boolean isEmpty()
{
return head == null;
}

public DoubleNode getHead()
{
return head;
}

public void insertHead(DoubleNode node)
{
if (isEmpty())
{
node.setPrev(null);
node.setNext(null);
head = node;
tail = node;
}
else
{
head.setPrev(node);
node.setPrev(null);
node.setNext(head);
head = node;
}
}

public void insertTail(DoubleNode node)
{
if (isEmpty())
{
node.setNext(null);
node.setPrev(null);
head = node;
tail = node;
}
else
{
tail.setNext(node);
node.setNext(null);
node.setPrev(tail);
tail = node;
}
}

public void deleteHead()
{
if (head.getNext() == null)
{
head = null;
tail = null;
}
else
{
head.getNext().setPrev(null);
head = head.getNext();
}
}

public void deleteTail()
{
if (head.getNext() == null)
{
head = null;
tail = null;
}
else
{
tail.getPrev().setNext(null);
tail = tail.getPrev();
}
}

public boolean insert(Event event)
{
DoubleNode newNode = new DoubleNode(event);
String timestamp = event.getTimestamp();
DoubleNode current = head;
boolean result = false;

while (current != null)
{
if (timestamp.compareTo(current.getEvent().getTimestamp()) < 0)
{
if (current == head)
{
insertHead(newNode);
}
else if (current == tail)
{
insertTail(newNode);
}
else
{
// insert the new node before the current node
newNode.setNext(current);
newNode.setPrev(current.getPrev());
current.getPrev().setNext(newNode);
current.setPrev(newNode);
}
result = true;
}
else
{
current = current.getNext();
}
}

if (current == null)
{
insertTail(newNode);
result = true;
}

return result;
}

public boolean delete(Event event)
{
DoubleNode current = head;
boolean result = false;
String timestamp = event.getTimestamp();

while (current != null)
{
if (timestamp.compareTo(current.getEvent().getTimestamp()) == 0)
{
// remove the node
result = true;
}
else
{
current = current.getNext();
}
}
return result;
}
}