implement AbstractTableModel for a Java collection

Question

I'm trying to implement an AbstractTableModel for a collection named "clients" but I keep receiving the error "required variable found value" for the "add" method. Here is my code:

I'm sorry for the confusion created. The add method is meant to add a new client in the table (by that I mean a new row). I don't want to add a new client to the collection.

class ModelTabel extends AbstractTableModel{

    public int getRowCount() {
        return clients.size();
    }

    public int getColumnCount() {
        return 4;
    }

    public Object getValueAt(int row, int column) {
        Client c = clients.get(row-1);
        switch(column){
            case 0: return c.getName();
            case 1: return c.getSurname();
            case 2: return c.getID();
            case 3: return c.getPhone();
            default:return "ERROR";
        }
    }

    public void add(Client c) {
        clients.get(clients.size()++) = a;
        fireTableDataChanged();
        }
    }

fireTableDataChanged(); is wrong notifier and reset whole model as is described in answer by @Ian Roberts, but all answer here going wrong way, your model is wrong, notifiers are wrong, you can to use any (theoretically) Java array as underlaying array for AbstractTableModel, there isn't reaquired to add elements in one array to model — mKorbel, Dec 19 '13 at 14:37

Prabhakaran Ramaswamy · Answer 1 · 2013-12-19T14:06:50.987

3

do like this

change

clients.get(clients.size()++) = a;

to

clients.add(c);

Now your method looks like

public void add(Client c) {
    clients.add(c); 
    fireTableDataChanged();
    }
}

Not sure how you getting clients.size(); believing clients Collection present in ModelTabel class.

edited Dec 19 '13 at 14:06

answered Dec 19 '13 at 13:59

Prabhakaran Ramaswamy

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I'm sorry for the confusion created. The add method is meant to add a new client in the table (by that I mean a new row). I don't want to add a new client to the collection. – bluesony Dec 19 '13 at 14:15

Ian Roberts · Answer 2 · 2013-12-19T14:06:11.297

3

You can't ++ the return value from a method, because the argument of ++ has to be something that is valid on the left hand side of an assignment. If you want to add something to the end of a Collection then the correct way to do that is to use the add method.

clients.add(a);

Also, you should fire a more specific modification event than simply "table changed". Calling fireTableDataChanged essentially tells listeners "the data in this model has changed beyond recognition, throw away your current visual representation and build a completely new one instead". It would be much more efficient and provide a better user experience if instead you used

fireTableRowsInserted(clients.size() - 1, clients.size() - 1);

which specifically says "one new row has been added to the end of this model, but the rest of the data is unchanged".

edited Dec 19 '13 at 14:06

answered Dec 19 '13 at 14:00

Ian Roberts

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(This is better than my answer) also - he doesn't say how the collection is initialized or accessed; if the collection is being added to outside the swing thread, then he probably needs to synchronize his list. One option: `clients = Collections.SynchronizedList(new ArrayList());` – JVMATL Dec 19 '13 at 14:10
+1 fireTableRowsInserted, but important is wrong model desing – mKorbel Dec 19 '13 at 14:36

Oliver Watkins · Answer 3 · 2013-12-19T14:09:25.433

Just keep it simple. You have an arraylist of clients right?

class ModelTabel extends AbstractTableModel{

    ArrayList<Client> clients = new ArrayList<Client>();

    public int getRowCount() {
        return clients.size();
    }

    public int getColumnCount() {
        return 4;
    }

    public Object getValueAt(int row, int column) {
        Client c = clients.get(row);
        switch(column){
            case 0: return c.getName();
            case 1: return c.getSurname();
            case 2: return c.getID();
            case 3: return c.getPhone();
            default:return "ERROR";
        }
    }

    public void add(Client c) {
        clients.add(c);
        fireTableDataChanged();
        }
    }

Yup, but it should be `ArrayList` – Gyro Gearless Dec 19 '13 at 14:07 — Gyro Gearless, Dec 19 '13 at 14:07

score 0 · Answer 4 · answered Dec 19 '13 at 13:56

Please show the full error message, not a paraphrasing of the error. Please show the line of text that causes the error.

Having said that, where is your clients variable? Where is it declared? Initialized? I think that your model needs this to work and to make sense.

score 0 · Accepted Answer · edited May 23 '17 at 12:11

I believe this is the same problem as this question... your variable assignment is reversed.

It should be (although this code is still incorrect - see below):

a = clients.get(clients.size()++);

EDIT: this was already answered by Prabhakaran, but apparently people felt the need to downvote my answer.. I think I did address the original question, but I appreciate that my code sample was still incorrect, so I will try to provide a more complete answer:

First of all, as to the "required variable not found" error, if you google it you will see that other SO question as the first hit. clients.get(clients.size()++) is not a variable, so you can't assign things to it. I am not sure where a is declared in your code, but assume that it is a variable and thus my suggestion of reversing the assignment.

Next, for the clients.get(clients.size()++) line, as others have mentioned or alluded to - VAR++ is equivalent to VAR = VAR + 1, so again is an assignment operation going on. In this case, clients.size() is not a variable, so you can not increment it. If you wanted the clients.size() + 1 index, you could have written: a = clients.get(clients.size() + 1)... but that will throw an ArrayIndexOutOfBoundsException, because you're trying to access an element of clients beyond its current size!

That is why Prabhakaran rewrote your method as they did, changing that line to a clients.add(c) call - as it seemed to fit the original intent of the method.

Indeed. Sorry, I only addressed the original question about the "required variable found value" error. — hineroptera, Dec 19 '13 at 14:10
Whoa! It actually worked with clients.add(c)! The only problem is that for every client I introduce, the table adds 2 rows with the same information. — bluesony, Dec 19 '13 at 14:45

JVMATL · Answer 6 · 2013-12-19T14:11:57.050

0

It would help if you show how your collection (I'm assuming it's a List? is being declared.

That being said, your add method doesn't make sense: I think you mean:

{
  clients.add( c );
  fireTableDataChanged()
}

edited Dec 19 '13 at 14:11

answered Dec 19 '13 at 14:05

JVMATL

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implement AbstractTableModel for a Java collection

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