Determine whether the linked list is a palindrome linked list

The first step is to put the values of the linked list in the array list , Then through the double pointer to determine whether it is a palindrome linked list , A pointer starts from scratch , The other pointer starts at the end , Traverse in turn , If the values encountered are different, return directly false, If the value is the same, continue to traverse , Until the two indexes meet .

First step ：

 List<Integer>  arr=new ArrayList<Integer>();
        ListNode currentNode=head;
        Boolean flag=true;
        while (currentNode!=null){
            arr.add(currentNode.val);
            currentNode=currentNode.next;
        }

The second step ：

 int front=0;
        int back=arr.size()-1;
        while (front<back){
            if (!arr.get(front).equals(arr.get(back))){
        flag=false;
            }
            front++;
            back--;
        }
        return  flag;