probem with populating JTable

[Pradeep Selvaraj]

Hello there,

I am just looking for populating JTable from the ArrayList.I am trying to do that by get a NullPointerException.

here is the code snippet

 
/* defining columns
Object dataValues[][];
String columnNames[];
 
String columnNames[] = { "Type",
  "Artist",
 "Title",
         "Product Info",
 "Price",
 "region",         "category"};
 
 for (int i = 0;i<list.size();i++)
 {
for (int index = 0;index<7;index++)
{
dataValues[i][index] =  this.addItems(i);
}
}
DefaultTableModel dtm = new DefaultTableModel(dataValues,columnNames);
jTable1 = new JTable(dtm);
 

/* addItems Method.........
private List addItems(int rec)
{
int i = rec;
List tempList = new ArrayList();
tempList.add(((Disk)list.get(i)).type);
tempList.add(((Disk)list.get(i)).artist_name);
tempList.add(((Disk)list.get(i)).title);
tempList.add(((Disk)list.get(i)).prod_no);
tempList.add(Double.toString(((Disk)list.get(i)).price));
tempList.add(((Disk)list.get(i)).region_encoding);
tempList.add(((Disk)list.get(i)).category);
return tempList;
}
 

Could any one plz help me out.Incase if my logic wrong can u guyz help me to populate records into JTABLE.

Thank you,

Pradeep

[Craig Wood]

Unless the Disk class has some method that returns its fields (instance variables) with an index or, as an array or, as a String that you can split into an array you'll have to hard–code the fields into the table columns as in the code below.

Instead of having the List list in class scope you could have createList return a reference to the list, ie

        ... in constructor
        List list = createList();
        Table table = getTable(list);
    ...
    private List createList()

and send it into the getTable method as an argument. Either way, a reference to list must be available inside the getTable method or you get a NullPointer. NullPointer means "we can't find it!".

The stack trace that starts with "NullPointerException" will tell you the line number where the exception was thrown. Just count down the lines in your source code file to find out where the exception was thrown.

class SomeClass
{
    List list;
 
    public SomeClass()
    {
        createList();
        JTable table = getTable();
        // load table into gui...
    }
 
    private void createList()
    {
        list = new ArrayList();
        // populate the list...
    }
 
    private JTable getTable()
    {
        // list must already exist and be populated
        // and must be available in class scope
        // or you can pass it in as an argument
        Object dataValues[][];
        String columnNames[];
 
        String columnNames[] = { "Type",
                                 "Artist",
                                 "Title",
                                 "Product Info",
                                 "Price",
                                 "region",
                                 "category" };
 
        for (int i = 0; i < list.size(); i++)
        {
            Disk disk = (Disk)list.get(i);
            dataValues[i][0] = disk.type;
            dataValues[i][1] = disk.artist_name;
            dataValues[i][2] = disk.title;
            dataValues[i][3] = disk.prod_no;
            dataValues[i][4] = String.valueOf(disk.price); // or leave as a double
            dataValues[i][5] = disk.region_encoding;
            dataValues[i][6] = disk.category;
        }
        DefaultTableModel dtm = new DefaultTableModel(dataValues, columnNames);
        JTable table = new JTable(dtm);
        return table;
    }
}

[Pradeep Selvaraj]

Thnx Craig.Thank you so much.It was really helpful.Your help is highly appreciated.