palindrome linked list

public ListNode (ListNode head) {
    ListNode slow = head, fast = head.next;
    while (fast != null && fast.next != null) {
        fast = fast.next.next;
        slow = slow.next;
    }
    return slow;
}

public boolean isPalindrome(ListNode head) {
    if (head == null || head.next == null)
        return true;
    ListNode slow = head, fast = head.next;
    while (fast != null && fast.next != null) {
        slow = slow.next;
        fast = fast.next.next;
    }
    ListNode newNode = reverse(slow.next);
    slow.next = null;
    while (head != null && newNode != null) {
        if (head.val != newNode.val)
            return false;
        head = head.next;
        newNode = newNode.next;
    }
    return true;
}

public ListNode reverse(ListNode head) {
    if (head == null || head.next == null)
        return head;
    ListNode prev = null;
    while (head != null) {
        ListNode tmp = head.next;
        head.next = prev;
        prev = head;
        head = tmp;
    }
    return prev;
}