remove duplicates from singly linked list

class LinkedList { 
  
    static Node head; 
  
    static class Node { 
  
        int data; 
        Node next; 
  
        Node(int d) { 
            data = d; 
            next = null; 
        } 
    } 
  
    /* Function to remove duplicates from an 
       unsorted linked list */
    void remove_duplicates() { 
        Node ptr1 = null, ptr2 = null, dup = null; 
        ptr1 = head; 
  
        /* Pick elements one by one */
        while (ptr1 != null && ptr1.next != null) { 
            ptr2 = ptr1; 
  
            /* Compare the picked element with rest 
                of the elements */
            while (ptr2.next != null) { 
  
                /* If duplicate then delete it */
                if (ptr1.data == ptr2.next.data) { 
  
                    /* sequence of steps is important here */
                    dup = ptr2.next; 
                    ptr2.next = ptr2.next.next; 
                    System.gc(); 
                } else /* This is tricky */ { 
                    ptr2 = ptr2.next; 
                } 
            } 
            ptr1 = ptr1.next; 
        } 
    } 
  
    void printList(Node node) { 
        while (node != null) { 
            System.out.print(node.data + " "); 
            node = node.next; 
        } 
    } 
  
    public static void main(String[] args) { 
        LinkedList list = new LinkedList(); 
        list.head = new Node(10); 
        list.head.next = new Node(12); 
        list.head.next.next = new Node(11); 
        list.head.next.next.next = new Node(11); 
        list.head.next.next.next.next = new Node(12); 
        list.head.next.next.next.next.next = new Node(11); 
        list.head.next.next.next.next.next.next = new Node(10); 
  
        System.out.println("Linked List before removing duplicates : \n "); 
        list.printList(head); 
  
        list.remove_duplicates(); 
        System.out.println(""); 
        System.out.println("Linked List after removing duplicates : \n "); 
        list.printList(head); 
    } 
}