Adding JComboBox[ ] at run time

Question

Hi All
I am using jdk 1.5. I am trying to add JComboBox array to JPanel
But whenever I create its object it gives me
NULL POINTER Exception
My code is as below
JComboBox comboarray[]=new JComboBox[ls.getItemCount()];
               System.out.println(""+comboarray[0].getName());
               JOptionPane.showMessageDialog(null, ls.getItemCount());
               for(int i=0;i<ls.getItemCount();i++)
                    comboarray.addItem(ls.getItems());
                    panel.add(comboarray[i]);
                    comboarray[i] = new JComboBox(ls.getItems());
What should be the problem ??
Thanking You
Regards
SGourav

Answer 1

Creating an array of objects (such as JComboBoxes) is not the same as creating an array of primitives, such as an int array. When you create an array of comboboxes (or other objects), you're really creating an array of references to comboboxes, and not the comboboxes themselves. To use the comboboxes in the array, you first have to create them. Think of it as if you were creating a parking lot. Even if you create the parking lot, you can't use any of the cars in the lot until you first fill the lot with cars.
So for an array of comboboxes, you'd do....
      JPanel comboPanel = new JPanel();
      JComboBox[] comboArray = new JComboBox[20];
      for (int i = 0; i < comboArray.length; i++) {
         comboArray[i] = new JComboBox();  // first create the object
         comboArray.addItem("foo " + i); // then and only then can you use it
comboPanel.add(comboArray[i]);