Java Linked List of Linked lists

Question

I'm currently building a program which requires me to use a Linked List of Linked Lists, and I have created my own linked list, but I don't know how to replace my object with a linked list. My current code is:

import java.io.Serializable;

class ListNode implements Serializable {
private static final long serialVersionUID = 8937086815484947032L;
private Client payload;
private ListNode next;

protected ListNode(Client payload) {
    this.payload = payload;
    this.next = null;
}

protected void setNext(ListNode next) {
    this.next = next;
}

protected ListNode getNext() {
    return next;
}

public String toString() {
    return payload.getClient();
}
}

public class OrderedLinkedList implements Serializable {
private static final long serialVersionUID = 7651599382448755370L;
private ListNode head;

public void add(String givenName, String surname) {
    ListNode newNode = new ListNode(new Client(givenName, surname));

    if (head != null)
        newNode.setNext(head);

    head = newNode;
}

public String toString() {
    ListNode iter = head;
    String collector = "";

    while (iter != null) {
        collector = collector + iter.toString();
        iter = iter.getNext();
    }

    return collector;
}

}

How do I make this linked list, show another linked list which then shows the object client. This is the code for object client

import java.io.Serializable;

public class Client implements Serializable {
private static final long serialVersionUID = 6472982140162477886L;
String givenName;
String surname;

public Client(String givenName, String surname) {
    this.givenName = givenName;
    this.surname = surname;
}

public String getClient() {
    StringBuilder sd = new StringBuilder();
    sd.append("First Name: ").append(givenName).append("\tSurname: ").append(surname).append("\n");

    return sd.toString();
}

}

I haven't used generics because I've never used them before and don't know how

Answer 1

I'm just unfolding the comments here:

That is how you make a LinkedList of LinkedLists:

 List<List<Client>> listOfLists= new LinkedList<List<Client>>();

Adding a new list:

  listOfLists.add(new LinkedList<Client>());

Adding an element:

listOfLists.get(0).add(new Client());

And don't forget the imports:

import java.util.List;
import java.util.LinkedList;