Reverse the List In Place

Reversing means re-aiming every next pointer at the node behind it instead of building a second list. The three cursors are already declared for you; the loop is yours.

Requirements:
1. reverse() flips the order of the existing nodes without creating any new Node.
2. Save the next node before you overwrite current.next, or the rest of the chain is lost.
3. When the loop ends, head must point at what used to be the last node. An empty or one-node list must survive unchanged.

The Node class is provided - do not rename it and do not add public to it, because a Java source file may contain only one public class.

Do NOT write a main method.