Question

I created a storage class and use to as the data type for my arraylist/Linked list.

private LinkedList bid_history;

I have initialised this in my constructure as

bid_history=new LinkedList <Bid_History> ();

I add new items to the list using add as illustrated below

bid_history.add(new Bid_History(bid_count,unit_price,bid_success));

After ‘n’ iterations I checked the contents of the list and found out that the list has ‘n’ elements but they were the same. i.e. the last element i added occupied the entire list. It is as if i added a reference variable to the list?

Any idea where I might have made a mistake? I also used an arraylist, the same problem. I am guessing I did something wrong with access specifiers! but I am out of ideas…..

—-Added ——-
I use a recursive function

bid()
{
   int bid,quantity;
        bid_success=false;
        bid_count++;
        System.out.println("Starting to bid, Bid ID:"+bid_count);
        quantity=(int)(rated_power*duration/60);
        if(bid_history.isEmpty())
        {
            unit_price=10;
        }
        else
        {
            unit_price++;
        }
        bid=unit_price*quantity;
        //Sending the calculated bid
        send_res(unit_price,quantity,500);
        long startTimeMs = System.currentTimeMillis( );
        System.out.println("Time:"+startTimeMs);
        while(!(System.currentTimeMillis( )>(startTimeMs+2000)));
        System.out.println("Time at end:"+System.currentTimeMillis( ));

        bid_history.add(new Bid_History(bid_count,unit_price,bid_success));

        if(bid_success!=true)
        {
            bid();
        }
}

the printing code is as follows

int count=0,size;
size=bid_history.size();
while(count<size)
System.out.println(((Bid_History)bid_history.get(count++)).getBid_amount());

Answer 1

Another possibility is that BidHistory(count, price, success) is not doing the right job and not setting the right fields. I don’t want to guess, but it might be that instead of having fields in BidHistory you are using static count/price/success fields in the class.

The constructor should look like (“this.” is important):

public BidHistory(int count, float price, boolean success) {
    this.count = count;
    this.price = price;
    this.success = success;
}