ArrayList copy some of the element from one arraylist tnto another arraylist

**ralf** · 07-07-2011, 07:07 PM

I have a method to to find which element in an arraylist that have not any value. The value of the element is null. When they are found they would be copied into a new arraylist.
I get an output which is very bad, the elements have been multiplied.
Like this:
Unsold [[1: chair (No bid), 2: can (No bid), 3: Doll Bid: 450, 4: Termo (No bid)]]
Unsold [[1: chair (No bid), 2: can (No bid), 3: Doll Bid: 450, 4: Termo (No bid)], [1: chair (No bid), 2: can (No bid), 3: Doll Bid: 450, 4: Termo (No bid)]]
Unsold [[1: chair (No bid), 2: can (No bid), 3: Doll Bid: 450, 4: Termo (No bid)], [1: chair (No bid), 2: can (No bid), 3: Doll Bid: 450, 4: Termo (No bid)], [1: chair

The output show also that it has been added more from the first arraylist than it should do.
I only want things like: Doll, can, Termo and chair to be copied into the new arraylist.

Some suggestion on what I can do to improve these two problems?

Java Code:

    public ArrayList getUnsold()
     {
         ArrayList unSold = new ArrayList();
         Iterator it = lots.iterator();
        while(it.hasNext())
        {                        
              Lot lot = (Lot) it.next(); //number, description, gethighestbid
                 if(lot.getHighestBid() == null)
                 {
                      unSold.add(lots); //It seems that every element are being added multplied times 
                      System.out.println("Unsold " + unSold); //during the iteration
                    }
           }
    return unSold;
    }

**Norm** · 07-07-2011, 07:31 PM

unSold.add(lots);

Is this what you want to do?

**ralf** · 07-07-2011, 07:51 PM

Hello,
I saw that and I have changed the code
The output is now see below:

Unsold [1: Hat (No bid), 2: Car (No bid), 3: Wood (No bid), 4: Termo Bid: 450]

I understand that it copy everything from lot to unsold, even those who have been bid on. that since I add from lot I think, but I thought the if test woudl filter it away

Java Code:

  public ArrayList getUnsold()
     {
         ArrayList unSold = new ArrayList();
         Iterator it = lots.iterator();
        while(it.hasNext())
        {                        
              Lot lot = (Lot) it.next(); //number, description, gethighestbid
                 if(lot.getHighestBid() == null)
                 {
                     // unSold.add(lot);
                      //System.out.println("Unsold " + unSold);
                    }
                              
                    unSold.add(lot);
                    
                } 
                 System.out.println("Unsold " + unSold);
    return unSold;
    }
 }

**Norm** · 07-07-2011, 08:05 PM

Is your code working as you want it now? Is the output correct?

Your posted code is very hard to read because the ending }s do NOT align beneath the corresponding beginning {s

It looks like the add() method is outside of the if statement's control.

**dlorde** · 07-07-2011, 08:20 PM

I'm assuming the code has an extra closing curly-brace because it's at the end of the class (or I don't see how it compiles), but whatever, as Norm says, your indentation is screwy - I think you've confused yourself with it, because unSold.add(lot); is actually outside of the null check (which, as posted, does nothing at all) so it gets called for every lot...

**ralf** · 07-07-2011, 08:24 PM

Hello again

The output is now:

Unsold [1: Car (No bid), 3: Cup (No bid)]
Is the code easier to read now? I added three lot and bidded on one of them, and now it return and print out just the two without ane bid on, so it seems correct.
Is there any way the lot could been copied without the number and the text (No bid)?

Java Code:

    public ArrayList getUnsold()
     {
         ArrayList unSold = new ArrayList();
         Iterator it = lots.iterator();
          while(it.hasNext())
           {                        
              Lot lot = (Lot) it.next(); //number, description, gethighestbid
                 if(lot.getHighestBid() == null)
                   {
                     unSold.add(lot);
                   }
     // unSold.add(lot);
           } 
 System.out.println("Unsold " + unSold);
    return unSold;

**dlorde** · 07-07-2011, 08:33 PM

Originally Posted by ralf

Is there any way the lot could been copied without the number and the text (No bid)?

I can't parse that - could you rephrase it more clearly?

**Norm** · 07-07-2011, 08:36 PM

Is there any way the lot could been copied without the number and the text (No bid)?

I think you are confusing what is printed when you print the unSold object: System.out.println("Unsold " + unSold);

with what the unSold list contains. The toString() method in the Lot class creates the output that is displayed when you print it.
For an easy test to see that, go to the Lot class and make a small change to the text that is returned by the toString() method and run your program again. You should see the change that you make on the print out.

**ralf** · 07-07-2011, 08:37 PM

Hello,

Yes, I mean if you see the output: Unsold [1: Car (No bid), 3: Cup (No bid)]

Everything from the first arraylist has been copied into the new one. Like 1: (No bid)
I was wondering if it could just copy the items like: Car, Cup?

**ralf** · 07-07-2011, 08:39 PM

Hello,

Yes, I mean if you see the output: Unsold [1: Car (No bid), 3: Cup (No bid)]

Everything from the first arraylist has been copied into the new one. Like 1: (No bid)
I was wondering if it could just copy the items like: Car, Cup?

**ralf** · 07-07-2011, 08:43 PM

Yes, you have right. I tested it. The return seems to work well. It return the correct number of lot.

Thanks, for the help!

**Norm** · 07-07-2011, 08:45 PM

You are copying the reference to a Lot object.
If you only what the contents of one of the variables in a Lot object, you need to change your code to copy just that variable instead of the whole Lot object.

**dlorde** · 07-07-2011, 08:49 PM

Originally Posted by ralf

Yes, I mean if you see the output: Unsold [1: Car (No bid), 3: Cup (No bid)]

Everything from the first arraylist has been copied into the new one.

No, only the unsold items have been copied. That's what you wanted, isn't it?

I was wondering if it could just copy the items like: Car, Cup?

If you just want to copy the names of the Lots, then just copy the names into the arraylist, but why? it doesn't save you anything - both Lots and Strings will be stored as references; you might just as well store the Lots.