Linking 2 Linked Lists together

[huiling25]

I have a Customer.java and a Transaction.java Transaction is when the user wants to deposit money. Customer.java includes the particulars of the user such as Name, AccountID, Balance etc. I have a LinkedList for Customer and a LinkedList for Transaction. How can i link the 2 together?

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//ListNode.java
public class ListNode{
    private Object item;
    private ListNode next,head;
    public ListNode(Object newItem)
    {    item = newItem;    next = null;     }
    public ListNode(Object newItem, ListNode newNext)
    {    item = newItem;    next = newNext;    }
    public void setItem(Object newItem)
    {    item = newItem;    }
    public void setNext(ListNode newNext)
    {    next = newNext;    }
    public Object getItem()
    {     return item;    }
    public ListNode getNext()
    {    return next;    }}
 
//LinkedList.java
public class LinkedList{
    protected ListNode head; //pointer to the first object
    protected int numOfItems; //total number of objects
    public LinkedList()
    {    head = null;     numOfItems = 0; }
    public boolean isEmptyList(){
        if(numOfItems==0)  return true;
        else    return false;    }
    protected ListNode find(int index) {   
         ListNode   cur = head;
         if (index > numOfItems) return null;
         for (int count=1; count<index; count++)     cur = cur.getNext();
         return cur;}
    public boolean insert(int at, Object newItem)
    {    ListNode   pre, cur;
         if (at < 1 || at > numOfItems+1) return false;
            numOfItems++;
         if (at == 1){
            if (isEmptyList()) head = new ListNode(newItem);
            else head = new ListNode(newItem, head);
            return true;}
        pre = find(at-1);
    cur = pre.getNext();
    pre.setNext(new ListNode(newItem, cur));
    return true;}
    public int size()
    {    return numOfItems;    }
 
//Customer.java
public class Customer{
    protected int acc_id;
    protected String name,address,birthdate,phone_no;
    protected double balance, interest;
    protected String type;
    public Customer(){....} //default constructor
    public Customer(int id,int name....){....}
    //all the set and get methods 
 
//Transaction
public class Transaction{
    protected int acc_id;
    protected String transDate,transTime;
    protected double amount;
    protected String type;
    protected int place;
public Transaction(){
    acc_id=0;
    transDate=null;
    transTime=null;
    type=null;
    place=0;}
public Transaction(int id,String d.....){
    acc_id=id;
    transDate = d;
    amount = amt; 
    type=typ;
    place=p;}
//all the set and get methods
 
//Main Program
 Customer[] records = new Customer[30];
LinkedList custRecords = new LinkedList();
ListNode numRecord = new ListNode(records);
//read from file and store into Customer array
//call insertTramsaction()
public static void insertTransaction(String filename, LinkedList list_record,Customer[] record){
        int i=0,j=0;
    Transaction[] trans = new Transaction[30];
 LinkedList transRecords = new LinkedList();
//store into trans array...
 for(i=0;i<trans.length;i++)
     transRecords.insert(i+1,trans[i]);
for(i=0;i<numRecords;i++){    
     for(j=0;j<numTrans;j++){
         if(trans[j].getID()==record[i].getID()){
                       //how to link to Customer LinkedList?
        }
    }
}
}//end program

I need to link Transaction LinkedList to Customer LinkedList, because each user have their own transaction records. So, i have to linked Transaction linked list to Customer linked list according to the user's account ID.