Kindly add the main method and print method to avoid confusion and add clarity.

public void printList(ListNode head) {
    ListNode current = head;
    while (current != null) {
        System.out.print(current.val + " ");
        current = current.next;
    }
    System.out.println();
}

public static void main(String[] args) {
    Solution solution = new Solution();
    
    // Test Example 1
    ListNode head1 = new ListNode(1, new ListNode(1, new ListNode(2)));
    ListNode result1 = solution.deleteDuplicates(head1); // Expected: 1 -> 2
    solution.printList(result1);

    // Test Example 2
    ListNode head2 = new ListNode(1, new ListNode(2, new ListNode(2, new ListNode(3))));
    ListNode result2 = solution.deleteDuplicates(head2); // Expected: 1 -> 2 -> 3
    solution.printList(result2);
    
    // Test Example 3
    ListNode head3 = new ListNode(3, new ListNode(3, new ListNode(3)));
    ListNode result3 = solution.deleteDuplicates(head3); // Expected: 3
    solution.printList(result3);
}