SinglyLinkedListReverse.java

package misc;

public class SinglyLinkedListReverse {

	public static void main(String[] args) {
		
		SinglyLinkedList.Node head = new SinglyLinkedList.Node(21);
		SinglyLinkedList linkedlist = new SinglyLinkedList(head);
		linkedlist.add(new SinglyLinkedList.Node(23));
		linkedlist.add(new SinglyLinkedList.Node(37));
		linkedlist.add(new SinglyLinkedList.Node(44));
		linkedlist.add(new SinglyLinkedList.Node(89));
		linkedlist.print();
		linkedlist.reverse(); 
		linkedlist.print();
	}
}

class SinglyLinkedList {
	static class Node {
		private int data;
		private Node next;
		
		public Node(int data) {
			this.data = data;
		}
		public int data() {
			return data;
		}
		public Node next() {
			return next;
		}
	}

	private Node head;
	public SinglyLinkedList(Node head) {
		this.head = head;
	}

	/** Java method to add an element to linked list */
	public void add(Node node) {
		Node current = head;
		while (current != null) {
			if (current.next == null) {
				current.next = node;
				break;
			}
			current = current.next;
		}
	}

	/** Java method to print a singly linked list */
	public void print() {
		Node node = head;
		while (node != null) {
			System.out.print(node.data() + " ");
			node = node.next();
		}
		System.out.println(" ");
	}

	/** Java method to reverse a linked list without recursion */
	public void reverse() {
		Node pointer = head;
		Node previous = null, current = null;
		while (pointer != null) {
			current = pointer;
			pointer = pointer.next;
			current.next = previous; // reverse the link
			previous = current;
			head = current;
		}
	}
}