ReverseLinkedList.java

class ListNode {
    int val;
    ListNode next;
    ListNode(int x) {
        val = x;
        next = null;
    }
}

public class ReverseLinkedList {
    public ListNode reverseList(ListNode head) {
        ListNode prev = null;
        ListNode curr = head;

        while (curr != null) {
            ListNode nextNode = curr.next;
            curr.next = prev;
            prev = curr;
            curr = nextNode;
        }

        return prev;
    }

    public static void main(String[] args) {
        
        ListNode head = new ListNode(1);
        head.next = new ListNode(2);
        head.next.next = new ListNode(3);
        head.next.next.next = new ListNode(4);
        head.next.next.next.next = new ListNode(5);

        ReverseLinkedList solution = new ReverseLinkedList();
        ListNode reversedHead = solution.reverseList(head);

        
        while (reversedHead != null) {
            System.out.print(reversedHead.val + " -> ");
            reversedHead = reversedHead.next;
        }
        System.out.println("null");
    }
}