java双向链表

public boolean putAfter(Object obj,DoublyListNode node)//有可能找不到obj,所以我返回boolean
{
DoublyListNode current = head;
while(head.obj!=obj){
current = current.next;
if(current==null)
return false;
}

if(current==tail){
node.next = null;
tail = node;
}else{
node.next = current.next;
current.next.previous = node;
}
node.previous = current;
current.next =node;
return true;
}
public DoublyListNode removeafter(Object obj){//返回了选中的节点
DoublyListNode current = head;
while(current.obj!=obj)
{
current = current.next;
if(current == null)
return null;
}
if(current==head)
head = current.next;
else
current.previous.next = current.next;
if(current == tail)
tail = current.previous;
else
current.next.previous = current.previous;
return current;
}