Putting ImageIcon Into Label (Original Size) By Clicking On Label (Thumbnail Created Before)

I'm doing a software Java GUI - JFrame form like this:

1. The user wants to click on a button that opens a bunch of images that will be displayed as thumbnail in the bottom of the JFrame .
2. Then the user wants to select/click one of the thumbnail and make appear the corresponding image in it's original size on above(center) of the JFrame.

For doing this I used 3 JPanel.

One contains a JButton that opens the jfilechoser dialog window,
the second "panelPreview" is for putting the thumbnails created,
and the third "panelGrande" is for the image in it's original size.

The firs part "1." is ok.

But in the second part : I got one error when I want to put the ImageIcon in to the JLabel with the further intent of displaying it.

lblBig(imgIcoVett[i]);

In this project I'm dealing with arrays of ImageIcons and JLabels, so it's a bit advanced level for me, so I'm not sure that I wrote right the part of the MouseListener too.

The error displayed by netbeans says "cannot find symbol symbol: method lbl (ImageIcon) local variables referenced from an inner class must be final or effectively final"

Here I attach the project I did with netbeans"AAAD Unlayout 2.zip", but if you just need the highlight of the code, here it is too:
 
private javax.swing.JButton btnOpenfile;
private javax.swing.JFileChooser jFileChooser1;
private javax.swing.JPanel jPanel1;
private javax.swing.JLabel lblBig;
private javax.swing.JPanel panelGrande;
private javax.swing.JPanel panelPreview;

[Code] ....